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Not able to get the result date/hours [duplicate]

How can I calculate an age in years, given a birth date of format YYYYMMDD? Is it possible using the Date() function?
I am looking for a better solution than the one I am using now:
var dob = '19800810';
var year = Number(dob.substr(0, 4));
var month = Number(dob.substr(4, 2)) - 1;
var day = Number(dob.substr(6, 2));
var today = new Date();
var age = today.getFullYear() - year;
if (today.getMonth() < month || (today.getMonth() == month && today.getDate() < day)) {
age--;
}
alert(age);

Try this.
function getAge(dateString) {
var today = new Date();
var birthDate = new Date(dateString);
var age = today.getFullYear() - birthDate.getFullYear();
var m = today.getMonth() - birthDate.getMonth();
if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) {
age--;
}
return age;
}
I believe the only thing that looked crude on your code was the substr part.
Fiddle: http://jsfiddle.net/codeandcloud/n33RJ/

I would go for readability:
function _calculateAge(birthday) { // birthday is a date
var ageDifMs = Date.now() - birthday.getTime();
var ageDate = new Date(ageDifMs); // miliseconds from epoch
return Math.abs(ageDate.getUTCFullYear() - 1970);
}
Disclaimer: This also has precision issues, so this cannot be completely trusted either. It can be off by a few hours, on some years, or during daylight saving (depending on timezone).
Instead I would recommend using a library for this, if precision is very important. Also #Naveens post, is probably the most accurate, as it doesn't rely on the time of day.

Important: This answer doesn't provide an 100% accurate answer, it is off by around 10-20 hours depending on the date.
There are no better solutions ( not in these answers anyway ). - naveen
I of course couldn't resist the urge to take up the challenge and make a faster and shorter birthday calculator than the current accepted solution.
The main point for my solution, is that math is fast, so instead of using branching, and the date model javascript provides to calculate a solution we use the wonderful math
The answer looks like this, and runs ~65% faster than naveen's plus it's much shorter:
function calcAge(dateString) {
var birthday = +new Date(dateString);
return ~~((Date.now() - birthday) / (31557600000));
}
The magic number: 31557600000 is 24 * 3600 * 365.25 * 1000
Which is the length of a year, the length of a year is 365 days and 6 hours which is 0.25 day. In the end i floor the result which gives us the final age.
Here is the benchmarks: http://jsperf.com/birthday-calculation
To support OP's data format you can replace +new Date(dateString);
with +new Date(d.substr(0, 4), d.substr(4, 2)-1, d.substr(6, 2));
If you can come up with a better solution please share! :-)

Clean one-liner solution using ES6:
const getAge = birthDate => Math.floor((new Date() - new Date(birthDate).getTime()) / 3.15576e+10)
// today is 2018-06-13
getAge('1994-06-14') // 23
getAge('1994-06-13') // 24
I am using a year of 365.25 days (0.25 because of leap years) which are 3.15576e+10 milliseconds (365.25 * 24 * 60 * 60 * 1000) respectively.
It has a few hours margin so depending on the use case it may not be the best option.

With momentjs:
/* The difference, in years, between NOW and 2012-05-07 */
moment().diff(moment('20120507', 'YYYYMMDD'), 'years')

Some time ago I made a function with that purpose:
function getAge(birthDate) {
var now = new Date();
function isLeap(year) {
return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
}
// days since the birthdate
var days = Math.floor((now.getTime() - birthDate.getTime())/1000/60/60/24);
var age = 0;
// iterate the years
for (var y = birthDate.getFullYear(); y <= now.getFullYear(); y++){
var daysInYear = isLeap(y) ? 366 : 365;
if (days >= daysInYear){
days -= daysInYear;
age++;
// increment the age only if there are available enough days for the year.
}
}
return age;
}
It takes a Date object as input, so you need to parse the 'YYYYMMDD' formatted date string:
var birthDateStr = '19840831',
parts = birthDateStr.match(/(\d{4})(\d{2})(\d{2})/),
dateObj = new Date(parts[1], parts[2]-1, parts[3]); // months 0-based!
getAge(dateObj); // 26

Here's my solution, just pass in a parseable date:
function getAge(birth) {
ageMS = Date.parse(Date()) - Date.parse(birth);
age = new Date();
age.setTime(ageMS);
ageYear = age.getFullYear() - 1970;
return ageYear;
// ageMonth = age.getMonth(); // Accurate calculation of the month part of the age
// ageDay = age.getDate(); // Approximate calculation of the day part of the age
}

Alternate solution, because why not:
function calculateAgeInYears (date) {
var now = new Date();
var current_year = now.getFullYear();
var year_diff = current_year - date.getFullYear();
var birthday_this_year = new Date(current_year, date.getMonth(), date.getDate());
var has_had_birthday_this_year = (now >= birthday_this_year);
return has_had_birthday_this_year
? year_diff
: year_diff - 1;
}

function age()
{
var birthdate = $j('#birthDate').val(); // in "mm/dd/yyyy" format
var senddate = $j('#expireDate').val(); // in "mm/dd/yyyy" format
var x = birthdate.split("/");
var y = senddate.split("/");
var bdays = x[1];
var bmonths = x[0];
var byear = x[2];
//alert(bdays);
var sdays = y[1];
var smonths = y[0];
var syear = y[2];
//alert(sdays);
if(sdays < bdays)
{
sdays = parseInt(sdays) + 30;
smonths = parseInt(smonths) - 1;
//alert(sdays);
var fdays = sdays - bdays;
//alert(fdays);
}
else{
var fdays = sdays - bdays;
}
if(smonths < bmonths)
{
smonths = parseInt(smonths) + 12;
syear = syear - 1;
var fmonths = smonths - bmonths;
}
else
{
var fmonths = smonths - bmonths;
}
var fyear = syear - byear;
document.getElementById('patientAge').value = fyear+' years '+fmonths+' months '+fdays+' days';
}

I think that could be simply like that:
function age(dateString){
let birth = new Date(dateString);
let now = new Date();
let beforeBirth = ((() => {birth.setDate(now.getDate());birth.setMonth(now.getMonth()); return birth.getTime()})() < birth.getTime()) ? 0 : 1;
return now.getFullYear() - birth.getFullYear() - beforeBirth;
}
age('09/20/1981');
//35
Works also with a timestamp
age(403501000000)
//34

That's the most elegant way for me:
const getAge = (birthDateString) => {
const today = new Date();
const birthDate = new Date(birthDateString);
const yearsDifference = today.getFullYear() - birthDate.getFullYear();
if (
today.getMonth() < birthDate.getMonth() ||
(today.getMonth() === birthDate.getMonth() && today.getDate() < birthDate.getDate())
) {
return yearsDifference - 1;
}
return yearsDifference;
};
console.log(getAge('2018-03-12'));

This question is over 10 years old an nobody has addressed the prompt that they already have the birth date in YYYYMMDD format?
If you have a past date and the current date both in YYYYMMDD format, you can very quickly calculate the number of years between them like this:
var pastDate = '20101030';
var currentDate = '20210622';
var years = Math.floor( ( currentDate - pastDate ) * 0.0001 );
// 10 (10.9592)
You can get the current date formatted as YYYYMMDD like this:
var now = new Date();
var currentDate = [
now.getFullYear(),
('0' + (now.getMonth() + 1) ).slice(-2),
('0' + now.getDate() ).slice(-2),
].join('');

To test whether the birthday already passed or not, I define a helper function Date.prototype.getDoY, which effectively returns the day number of the year. The rest is pretty self-explanatory.
Date.prototype.getDoY = function() {
var onejan = new Date(this.getFullYear(), 0, 1);
return Math.floor(((this - onejan) / 86400000) + 1);
};
function getAge(birthDate) {
function isLeap(year) {
return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
}
var now = new Date(),
age = now.getFullYear() - birthDate.getFullYear(),
doyNow = now.getDoY(),
doyBirth = birthDate.getDoY();
// normalize day-of-year in leap years
if (isLeap(now.getFullYear()) && doyNow > 58 && doyBirth > 59)
doyNow--;
if (isLeap(birthDate.getFullYear()) && doyNow > 58 && doyBirth > 59)
doyBirth--;
if (doyNow <= doyBirth)
age--; // birthday not yet passed this year, so -1
return age;
};
var myBirth = new Date(2001, 6, 4);
console.log(getAge(myBirth));

I just had to write this function for myself - the accepted answer is fairly good but IMO could use some cleanup. This takes a unix timestamp for dob because that was my requirement but could be quickly adapted to use a string:
var getAge = function(dob) {
var measureDays = function(dateObj) {
return 31*dateObj.getMonth()+dateObj.getDate();
},
d = new Date(dob*1000),
now = new Date();
return now.getFullYear() - d.getFullYear() - (measureDays(now) < measureDays(d));
}
Notice I've used a flat value of 31 in my measureDays function. All the calculation cares about is that the "day-of-year" be a monotonically increasing measure of the timestamp.
If using a javascript timestamp or string, obviously you'll want to remove the factor of 1000.

function getAge(dateString) {
var dates = dateString.split("-");
var d = new Date();
var userday = dates[0];
var usermonth = dates[1];
var useryear = dates[2];
var curday = d.getDate();
var curmonth = d.getMonth()+1;
var curyear = d.getFullYear();
var age = curyear - useryear;
if((curmonth < usermonth) || ( (curmonth == usermonth) && curday < userday )){
age--;
}
return age;
}
To get the age when european date has entered:
getAge('16-03-1989')

I've checked the examples showed before and they didn't worked in all cases, and because of this i made a script of my own. I tested this, and it works perfectly.
function getAge(birth) {
var today = new Date();
var curr_date = today.getDate();
var curr_month = today.getMonth() + 1;
var curr_year = today.getFullYear();
var pieces = birth.split('/');
var birth_date = pieces[0];
var birth_month = pieces[1];
var birth_year = pieces[2];
if (curr_month == birth_month && curr_date >= birth_date) return parseInt(curr_year-birth_year);
if (curr_month == birth_month && curr_date < birth_date) return parseInt(curr_year-birth_year-1);
if (curr_month > birth_month) return parseInt(curr_year-birth_year);
if (curr_month < birth_month) return parseInt(curr_year-birth_year-1);
}
var age = getAge('18/01/2011');
alert(age);

Get the age (years, months and days) from the date of birth with javascript
Function calcularEdad (years, months and days)
function calcularEdad(fecha) {
// Si la fecha es correcta, calculamos la edad
if (typeof fecha != "string" && fecha && esNumero(fecha.getTime())) {
fecha = formatDate(fecha, "yyyy-MM-dd");
}
var values = fecha.split("-");
var dia = values[2];
var mes = values[1];
var ano = values[0];
// cogemos los valores actuales
var fecha_hoy = new Date();
var ahora_ano = fecha_hoy.getYear();
var ahora_mes = fecha_hoy.getMonth() + 1;
var ahora_dia = fecha_hoy.getDate();
// realizamos el calculo
var edad = (ahora_ano + 1900) - ano;
if (ahora_mes < mes) {
edad--;
}
if ((mes == ahora_mes) && (ahora_dia < dia)) {
edad--;
}
if (edad > 1900) {
edad -= 1900;
}
// calculamos los meses
var meses = 0;
if (ahora_mes > mes && dia > ahora_dia)
meses = ahora_mes - mes - 1;
else if (ahora_mes > mes)
meses = ahora_mes - mes
if (ahora_mes < mes && dia < ahora_dia)
meses = 12 - (mes - ahora_mes);
else if (ahora_mes < mes)
meses = 12 - (mes - ahora_mes + 1);
if (ahora_mes == mes && dia > ahora_dia)
meses = 11;
// calculamos los dias
var dias = 0;
if (ahora_dia > dia)
dias = ahora_dia - dia;
if (ahora_dia < dia) {
ultimoDiaMes = new Date(ahora_ano, ahora_mes - 1, 0);
dias = ultimoDiaMes.getDate() - (dia - ahora_dia);
}
return edad + " años, " + meses + " meses y " + dias + " días";
}
Function esNumero
function esNumero(strNumber) {
if (strNumber == null) return false;
if (strNumber == undefined) return false;
if (typeof strNumber === "number" && !isNaN(strNumber)) return true;
if (strNumber == "") return false;
if (strNumber === "") return false;
var psInt, psFloat;
psInt = parseInt(strNumber);
psFloat = parseFloat(strNumber);
return !isNaN(strNumber) && !isNaN(psFloat);
}

One more possible solution with moment.js:
var moment = require('moment');
var startDate = new Date();
var endDate = new Date();
endDate.setDate(endDate.getFullYear() + 5); // Add 5 years to second date
console.log(moment.duration(endDate - startDate).years()); // This should returns 5

I am a bit too late but I found this to be the simplest way to calculate a birth date.
Hopefully this will help.
function init() {
writeYears("myage", 0, Age());
}
function Age() {
var birthday = new Date(1997, 02, 01), //Year, month-1 , day.
today = new Date(),
one_year = 1000 * 60 * 60 * 24 * 365;
return Math.floor((today.getTime() - birthday.getTime()) / one_year);
}
function writeYears(id, current, maximum) {
document.getElementById(id).innerHTML = current;
if (current < maximum) {
setTimeout(function() {
writeYears(id, ++current, maximum);
}, Math.sin(current / maximum) * 200);
}
}
init()
<span id="myage"></span>

Works perfect for me, guys.
getAge(birthday) {
const millis = Date.now() - Date.parse(birthday);
return new Date(millis).getFullYear() - 1970;
}

I know this is a very old thread but I wanted to put in this implementation that I wrote for finding the age which I believe is much more accurate.
var getAge = function(year,month,date){
var today = new Date();
var dob = new Date();
dob.setFullYear(year);
dob.setMonth(month-1);
dob.setDate(date);
var timeDiff = today.valueOf() - dob.valueOf();
var milliInDay = 24*60*60*1000;
var noOfDays = timeDiff / milliInDay;
var daysInYear = 365.242;
return ( noOfDays / daysInYear ) ;
}
Ofcourse you could adapt this to fit in other formats of getting the parameters. Hope this helps someone looking for a better solution.

I used this approach using logic instead of math.
It's precise and quick.
The parameters are the year, month and day of the person's birthday.
It returns the person's age as an integer.
function calculateAge(year, month, day) {
var currentDate = new Date();
var currentYear = currentDate.getFullYear();
var currentMonth = currentDate.getUTCMonth() + 1;
var currentDay = currentDate.getUTCDate();
// You need to treat the cases where the year, month or day hasn't arrived yet.
var age = currentYear - year;
if (currentMonth > month) {
return age;
} else {
if (currentDay >= day) {
return age;
} else {
age--;
return age;
}
}
}

Adopting from naveen's and original OP's posts I ended up with a reusable method stub that accepts both strings and / or JS Date objects.
I named it gregorianAge() because this calculation gives exactly how we denote age using Gregorian calendar. i.e. Not counting the end year if month and day is before the month and day of the birth year.
/**
* Calculates human age in years given a birth day. Optionally ageAtDate
* can be provided to calculate age at a specific date
*
* #param string|Date Object birthDate
* #param string|Date Object ageAtDate optional
* #returns integer Age between birthday and a given date or today
*/
function gregorianAge(birthDate, ageAtDate) {
// convert birthDate to date object if already not
if (Object.prototype.toString.call(birthDate) !== '[object Date]')
birthDate = new Date(birthDate);
// use today's date if ageAtDate is not provided
if (typeof ageAtDate == "undefined")
ageAtDate = new Date();
// convert ageAtDate to date object if already not
else if (Object.prototype.toString.call(ageAtDate) !== '[object Date]')
ageAtDate = new Date(ageAtDate);
// if conversion to date object fails return null
if (ageAtDate == null || birthDate == null)
return null;
var _m = ageAtDate.getMonth() - birthDate.getMonth();
// answer: ageAt year minus birth year less one (1) if month and day of
// ageAt year is before month and day of birth year
return (ageAtDate.getFullYear()) - birthDate.getFullYear()
- ((_m < 0 || (_m === 0 && ageAtDate.getDate() < birthDate.getDate())) ? 1 : 0)
}
// Below is for the attached snippet
function showAge() {
$('#age').text(gregorianAge($('#dob').val()))
}
$(function() {
$(".datepicker").datepicker();
showAge();
});
<link rel="stylesheet" href="//code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.css">
<script src="//code.jquery.com/jquery-1.10.2.js"></script>
<script src="//code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
DOB:
<input name="dob" value="12/31/1970" id="dob" class="datepicker" onChange="showAge()" /> AGE: <span id="age"><span>

Two more options:
// Int Age to Date as string YYY-mm-dd
function age_to_date(age)
{
try {
var d = new Date();
var new_d = '';
d.setFullYear(d.getFullYear() - Math.abs(age));
new_d = d.getFullYear() + '-' + d.getMonth() + '-' + d.getDate();
return new_d;
} catch(err) {
console.log(err.message);
}
}
// Date string (YYY-mm-dd) to Int age (years old)
function date_to_age(date)
{
try {
var today = new Date();
var d = new Date(date);
var year = today.getFullYear() - d.getFullYear();
var month = today.getMonth() - d.getMonth();
var day = today.getDate() - d.getDate();
var carry = 0;
if (year < 0)
return 0;
if (month <= 0 && day <= 0)
carry -= 1;
var age = parseInt(year);
age += carry;
return Math.abs(age);
} catch(err) {
console.log(err.message);
}
}

I've did some updated to one previous answer.
var calculateAge = function(dob) {
var days = function(date) {
return 31*date.getMonth() + date.getDate();
},
d = new Date(dob*1000),
now = new Date();
return now.getFullYear() - d.getFullYear() - ( measureDays(now) < measureDays(d));
}
I hope that helps :D

here is a simple way of calculating age:
//dob date dd/mm/yy
var d = 01/01/1990
//today
//date today string format
var today = new Date(); // i.e wed 04 may 2016 15:12:09 GMT
//todays year
var todayYear = today.getFullYear();
// today month
var todayMonth = today.getMonth();
//today date
var todayDate = today.getDate();
//dob
//dob parsed as date format
var dob = new Date(d);
// dob year
var dobYear = dob.getFullYear();
// dob month
var dobMonth = dob.getMonth();
//dob date
var dobDate = dob.getDate();
var yearsDiff = todayYear - dobYear ;
var age;
if ( todayMonth < dobMonth )
{
age = yearsDiff - 1;
}
else if ( todayMonth > dobMonth )
{
age = yearsDiff ;
}
else //if today month = dob month
{ if ( todayDate < dobDate )
{
age = yearsDiff - 1;
}
else
{
age = yearsDiff;
}
}

var now = DateTime.Now;
var age = DateTime.Now.Year - dob.Year;
if (now.Month < dob.Month || now.Month == dob.Month && now.Day < dob.Day) age--;

You may use this for age restriction in your form -
function dobvalidator(birthDateString){
strs = birthDateString.split("-");
var dd = strs[0];
var mm = strs[1];
var yy = strs[2];
var d = new Date();
var ds = d.getDate();
var ms = d.getMonth();
var ys = d.getFullYear();
var accepted_age = 18;
var days = ((accepted_age * 12) * 30) + (ms * 30) + ds;
var age = (((ys - yy) * 12) * 30) + ((12 - mm) * 30) + parseInt(30 - dd);
if((days - age) <= '0'){
console.log((days - age));
alert('You are at-least ' + accepted_age);
}else{
console.log((days - age));
alert('You are not at-least ' + accepted_age);
}
}

This is my modification:
function calculate_age(date) {
var today = new Date();
var today_month = today.getMonth() + 1; //STRANGE NUMBERING //January is 0!
var age = today.getYear() - date.getYear();
if ((today_month > date.getMonth() || ((today_month == date.getMonth()) && (today.getDate() < date.getDate())))) {
age--;
}
return age;
};

I believe that sometimes the readability is more important in this case. Unless we are validating 1000s of fields, this should be accurate and fast enough:
function is18orOlder(dateString) {
const dob = new Date(dateString);
const dobPlus18 = new Date(dob.getFullYear() + 18, dob.getMonth(), dob.getDate());
return dobPlus18 .valueOf() <= Date.now();
}
// Testing:
console.log(is18orOlder('01/01/1910')); // true
console.log(is18orOlder('01/01/2050')); // false
// When I'm posting this on 10/02/2020, so:
console.log(is18orOlder('10/08/2002')); // true
console.log(is18orOlder('10/19/2002')) // false
I like this approach instead of using a constant for how many ms are in a year, and later messing with the leap years, etc. Just letting the built-in Date to do the job.
Update, posting this snippet since one may found it useful. Since I'm enforcing a mask on the input field, to have the format of mm/dd/yyyy and already validating if the date is valid, in my case, this works too to validate 18+ years:
function is18orOlder(dateString) {
const [month, date, year] = value.split('/');
return new Date(+year + 13, +month, +date).valueOf() <= Date.now();
}

jquery new date() 12 hour format [duplicate]

How do you display a JavaScript datetime object in the 12 hour format (AM/PM)?

function formatAMPM(date) {
var hours = date.getHours();
var minutes = date.getMinutes();
var ampm = hours >= 12 ? 'pm' : 'am';
hours = hours % 12;
hours = hours ? hours : 12; // the hour '0' should be '12'
minutes = minutes < 10 ? '0'+minutes : minutes;
var strTime = hours + ':' + minutes + ' ' + ampm;
return strTime;
}
console.log(formatAMPM(new Date));

If you just want to show the hours then..
var time = new Date();
console.log(
time.toLocaleString('en-US', { hour: 'numeric', hour12: true })
);
Output : 7 AM
If you wish to show the minutes as well then...
var time = new Date();
console.log(
time.toLocaleString('en-US', { hour: 'numeric', minute: 'numeric', hour12: true })
);
Output : 7:23 AM

Here's a way using regex:
console.log(new Date('7/10/2013 20:12:34').toLocaleTimeString().replace(/([\d]+:[\d]{2})(:[\d]{2})(.*)/, "$1$3"))
console.log(new Date('7/10/2013 01:12:34').toLocaleTimeString().replace(/([\d]+:[\d]{2})(:[\d]{2})(.*)/, "$1$3"))
This creates 3 matching groups:
([\d]+:[\d]{2}) - Hour:Minute
(:[\d]{2}) - Seconds
(.*) - the space and period (Period is the official name for AM/PM)
Then it displays the 1st and 3rd groups.
WARNING: toLocaleTimeString() may behave differently based on region / location.

If you don't need to print the am/pm, I found the following nice and concise:
var now = new Date();
var hours = now.getHours() % 12 || 12; // 12h instead of 24h, with 12 instead of 0.
This is based off #bbrame's answer.

As far as I know, the best way to achieve that without extensions and complex coding is like this:
date.toLocaleString([], { hour12: true});
Javascript AM/PM Format
<!DOCTYPE html>
<html>
<body>
<p>Click the button to display the date and time as a string.</p>
<button onclick="myFunction()">Try it</button>
<button onclick="fullDateTime()">Try it2</button>
<p id="demo"></p>
<p id="demo2"></p>
<script>
function myFunction() {
var d = new Date();
var n = d.toLocaleString([], { hour: '2-digit', minute: '2-digit' });
document.getElementById("demo").innerHTML = n;
}
function fullDateTime() {
var d = new Date();
var n = d.toLocaleString([], { hour12: true});
document.getElementById("demo2").innerHTML = n;
}
</script>
</body>
</html>
I found this checking this question out.
How do I use .toLocaleTimeString() without displaying seconds?

In modern browsers, use Intl.DateTimeFormat and force 12hr format with options:
let now = new Date();
new Intl.DateTimeFormat('default',
{
hour12: true,
hour: 'numeric',
minute: 'numeric'
}).format(now);
// 6:30 AM
Using default will honor browser's default locale if you add more options, yet will still output 12hr format.

Use Moment.js for this
Use below codes in JavaScript when using moment.js
H, HH 24 hour time
h, or hh 12 hour time (use in conjunction with a or A)
The format() method returns the date in specific format.
moment(new Date()).format("YYYY-MM-DD HH:mm"); // 24H clock
moment(new Date()).format("YYYY-MM-DD hh:mm A"); // 12H clock (AM/PM)
moment(new Date()).format("YYYY-MM-DD hh:mm a"); // 12H clock (am/pm)

My suggestion is use moment js for date and time operation.
https://momentjs.com/docs/#/displaying/format/
console.log(moment().format('hh:mm a'));
<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment.min.js"></script>

Updated for more compression
const formatAMPM = (date) => {
let hours = date.getHours();
let minutes = date.getMinutes();
const ampm = hours >= 12 ? 'pm' : 'am';
hours %= 12;
hours = hours || 12;
minutes = minutes < 10 ? `0${minutes}` : minutes;
const strTime = `${hours}:${minutes} ${ampm}`;
return strTime;
};
console.log(formatAMPM(new Date()));

use dateObj.toLocaleString([locales[, options]])
Option 1 - Using locales
var date = new Date();
console.log(date.toLocaleString('en-US'));
Option 2 - Using options
var options = { hour12: true };
console.log(date.toLocaleString('en-GB', options));
Note: supported on all browsers but safari atm

Short RegExp for en-US:
var d = new Date();
d = d.toLocaleTimeString().replace(/:\d+ /, ' '); // current time, e.g. "1:54 PM"

Please find the solution below
var d = new Date();
var amOrPm = (d.getHours() < 12) ? "AM" : "PM";
var hour = (d.getHours() < 12) ? d.getHours() : d.getHours() - 12;
return d.getDate() + ' / ' + d.getMonth() + ' / ' + d.getFullYear() + ' ' + hour + ':' + d.getMinutes() + ' ' + amOrPm;

It will return the following format like
09:56 AM
appending zero in start for the hours as well if it is less than 10
Here it is using ES6 syntax
const getTimeAMPMFormat = (date) => {
let hours = date.getHours();
let minutes = date.getMinutes();
const ampm = hours >= 12 ? 'PM' : 'AM';
hours = hours % 12;
hours = hours ? hours : 12; // the hour '0' should be '12'
hours = hours < 10 ? '0' + hours : hours;
// appending zero in the start if hours less than 10
minutes = minutes < 10 ? '0' + minutes : minutes;
return hours + ':' + minutes + ' ' + ampm;
};
console.log(getTimeAMPMFormat(new Date)); // 09:59 AM

I fount it's here it working fine.
var date_format = '12'; /* FORMAT CAN BE 12 hour (12) OR 24 hour (24)*/
var d = new Date();
var hour = d.getHours(); /* Returns the hour (from 0-23) */
var minutes = d.getMinutes(); /* Returns the minutes (from 0-59) */
var result = hour;
var ext = '';
if(date_format == '12'){
if(hour > 12){
ext = 'PM';
hour = (hour - 12);
result = hour;
if(hour < 10){
result = "0" + hour;
}else if(hour == 12){
hour = "00";
ext = 'AM';
}
}
else if(hour < 12){
result = ((hour < 10) ? "0" + hour : hour);
ext = 'AM';
}else if(hour == 12){
ext = 'PM';
}
}
if(minutes < 10){
minutes = "0" + minutes;
}
result = result + ":" + minutes + ' ' + ext;
console.log(result);
and plunker example here

Check out Datejs. Their built in formatters can do this: http://code.google.com/p/datejs/wiki/APIDocumentation#toString
It's a really handy library, especially if you are planning on doing other things with date objects.

<script>
var todayDate = new Date();
var getTodayDate = todayDate.getDate();
var getTodayMonth = todayDate.getMonth()+1;
var getTodayFullYear = todayDate.getFullYear();
var getCurrentHours = todayDate.getHours();
var getCurrentMinutes = todayDate.getMinutes();
var getCurrentAmPm = getCurrentHours >= 12 ? 'PM' : 'AM';
getCurrentHours = getCurrentHours % 12;
getCurrentHours = getCurrentHours ? getCurrentHours : 12;
getCurrentMinutes = getCurrentMinutes < 10 ? '0'+getCurrentMinutes : getCurrentMinutes;
var getCurrentDateTime = getTodayDate + '-' + getTodayMonth + '-' + getTodayFullYear + ' ' + getCurrentHours + ':' + getCurrentMinutes + ' ' + getCurrentAmPm;
alert(getCurrentDateTime);
</script>

Hopefully this answer is a little more readable than the other answers (especially for new comers).
Here's the solution I've implemented in some of my sites for informing the last time the site code was modified. It implements AM/PM time through the options parameter of date.toLocaleDateString (see related Mozilla documentation).
// Last time page code was updated/changed
const options = {
year: "numeric",
month: "long",
weekday: "long",
day: "numeric",
hour: "numeric",
minute: "numeric",
second: "numeric",
hour12: true // This is the line of code we care about here
/*
false: displays 24hs format for time
true: displays 12, AM and PM format
*/
};
let last = document.lastModified;
let date = new Date(last);
let local = date.toLocaleDateString("en-US", options);
let fullDate = `${local}`;
document.getElementById("updated").textContent = fullDate;
Which output is in the format:
Saturday, May 28, 2022, 8:38:50 PM
This output is then displayed in the following HTML code:
<p>Last update: <span id="updated">_update_date_goes_here</span></p>
NOTE: In this use case, document.lastModified has some weird behaviors depending if it's run locally or on a external server (see this Stack Overflow question). Though it works correctly when I run it in my GitHub page (you should see it in action in the site at the footer).

Here is another way that is simple, and very effective:
var d = new Date();
var weekday = new Array(7);
weekday[0] = "Sunday";
weekday[1] = "Monday";
weekday[2] = "Tuesday";
weekday[3] = "Wednesday";
weekday[4] = "Thursday";
weekday[5] = "Friday";
weekday[6] = "Saturday";
var month = new Array(11);
month[0] = "January";
month[1] = "February";
month[2] = "March";
month[3] = "April";
month[4] = "May";
month[5] = "June";
month[6] = "July";
month[7] = "August";
month[8] = "September";
month[9] = "October";
month[10] = "November";
month[11] = "December";
var t = d.toLocaleTimeString().replace(/:\d+ /, ' ');
document.write(weekday[d.getDay()] + ',' + " " + month[d.getMonth()] + " " + d.getDate() + ',' + " " + d.getFullYear() + '<br>' + d.toLocaleTimeString());
</script></div><!-- #time -->

you can determine am or pm with this simple code
var today=new Date();
var noon=new Date(today.getFullYear(),today.getMonth(),today.getDate(),12,0,0);
var ampm = (today.getTime()<noon.getTime())?'am':'pm';

try this
var date = new Date();
var hours = date.getHours();
var minutes = date.getMinutes();
var seconds = date.getSeconds();
var ampm = hours >= 12 ? "pm" : "am";

function formatTime( d = new Date(), ampm = true )
{
var hour = d.getHours();
if ( ampm )
{
var a = ( hour >= 12 ) ? 'PM' : 'AM';
hour = hour % 12;
hour = hour ? hour : 12; // the hour '0' should be '12'
}
var hour = checkDigit(hour);
var minute = checkDigit(d.getMinutes());
var second = checkDigit(d.getSeconds());
// https://stackoverflow.com/questions/1408289/how-can-i-do-string-interpolation-in-javascript
return ( ampm ) ? `${hour}:${minute}:${second} ${a}` : `${hour}:${minute}:${second}`;
}
function checkDigit(t)
{
return ( t < 10 ) ? `0${t}` : t;
}
document.querySelector("#time1").innerHTML = formatTime();
document.querySelector("#time2").innerHTML = formatTime( new Date(), false );
<p>ampm true: <span id="time1"></span> (default)</p>
<p>ampm false: <span id="time2"></span></p>

function startTime() {
const today = new Date();
let h = today.getHours();
let m = today.getMinutes();
let s = today.getSeconds();
var meridian = h >= 12 ? "PM" : "AM";
h = h % 12;
h = h ? h : 12;
m = m < 10 ? "0" + m : m;
s = s < 10 ? "0" + s : s;
var strTime = h + ":" + m + ":" + s + " " + meridian;
document.getElementById('time').innerText = strTime;
setTimeout(startTime, 1000);
}
startTime();
<h1 id='time'></h1>

If you have time as string like so var myTime = "15:30",
then you can use the following code to get am pm.
var hour = parseInt(myTime.split(":")[0]) % 12;
var timeInAmPm = (hour == 0 ? "12": hour ) + ":" + myTime.split(":")[1] + " " + (parseInt(parseInt(myTime.split(":")[0]) / 12) < 1 ? "am" : "pm");

var d = new Date();
var hours = d.getHours() % 12;
hours = hours ? hours : 12;
var test = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'][(d.getMonth() + 1)] + " " +
("00" + d.getDate()).slice(-2) + " " +
d.getFullYear() + " " +
("00" + hours).slice(-2) + ":" +
("00" + d.getMinutes()).slice(-2) + ":" +
("00" + d.getSeconds()).slice(-2) + ' ' + (d.getHours() >= 12 ? 'PM' : 'AM');
document.getElementById("demo").innerHTML = test;
<p id="demo" ></p>

<h1 id="clock_display" class="text-center" style="font-size:40px; color:#ffffff">[CLOCK TIME DISPLAYS HERE]</h1>
<script>
var AM_or_PM = "AM";
function startTime(){
var today = new Date();
var h = today.getHours();
var m = today.getMinutes();
var s = today.getSeconds();
h = twelve_hour_time(h);
m = checkTime(m);
s = checkTime(s);
document.getElementById('clock_display').innerHTML =
h + ":" + m + ":" + s +" "+AM_or_PM;
var t = setTimeout(startTime, 1000);
}
function checkTime(i){
if(i < 10){
i = "0" + i;// add zero in front of numbers < 10
}
return i;
}
// CONVERT TO 12 HOUR TIME. SET AM OR PM
function twelve_hour_time(h){
if(h > 12){
h = h - 12;
AM_or_PM = " PM";
}
return h;
}
startTime();
</script>

function getDateTime() {
var now = new Date();
var year = now.getFullYear();
var month = now.getMonth() + 1;
var day = now.getDate();
if (month.toString().length == 1) {
month = '0' + month;
}
if (day.toString().length == 1) {
day = '0' + day;
}
var hours = now.getHours();
var minutes = now.getMinutes();
var ampm = hours >= 12 ? 'pm' : 'am';
hours = hours % 12;
hours = hours ? hours : 12;
minutes = minutes < 10 ? '0' + minutes : minutes;
var timewithampm = hours + ':' + minutes + ' ' + ampm;
var dateTime = monthNames[parseInt(month) - 1] + ' ' + day + ' ' + year + ' ' + timewithampm;
return dateTime;
}

Here my solution
function getTime() {
var systemDate = new Date();
var hours = systemDate.getHours();
var minutes = systemDate.getMinutes();
var strampm;
if (hours >= 12) {
strampm= "PM";
} else {
strampm= "AM";
}
hours = hours % 12;
if (hours == 0) {
hours = 12;
}
_hours = checkTimeAddZero(hours);
_minutes = checkTimeAddZero(minutes);
console.log(_hours + ":" + _minutes + " " + strampm);
}
function checkTimeAddZero(i) {
if (i < 10) {
i = "0" + i
}
return i;
}

const formatAMPM = (date) => {
try {
let time = date.split(" ");
let hours = time[4].split(":")[0];
let minutes = time[4].split(":")[1];
hours = hours || 12;
const ampm = hours >= 12 ? " PM" : " AM";
minutes = minutes < 10 ? `${minutes}` : minutes;
hours %= 12;
const strTime = `${hours}:${minutes} ${ampm}`;
return strTime;
} catch (e) {
return "";
}
};
const startTime = "2021-12-07T17:00:00.073Z"
formatAMPM(new Date(startTime).toUTCString())

This is the easiest Way you can Achieve this using ternary operator or you can also use if else instead !
const d = new Date();
let hrs = d.getHours();
let m = d.getMinutes();
// Condition to add zero before minute
let min = m < 10 ? `0${m}` : m;
const currTime = hrs >= 12 ? `${hrs - 12}:${min} pm` : `${hrs}:${min} am`;
console.log(currTime);

Or just simply do the following code:
<script>
time = function() {
var today = new Date();
var h = today.getHours();
var m = today.getMinutes();
var s = today.getSeconds();
m = checkTime(m);
s = checkTime(s);
document.getElementById('txt_clock').innerHTML = h + ":" + m + ":" + s;
var t = setTimeout(function(){time()}, 0);
}
time2 = function() {
var today = new Date();
var h = today.getHours();
var m = today.getMinutes();
var s = today.getSeconds();
m = checkTime(m);
s = checkTime(s);
if (h>12) {
document.getElementById('txt_clock_stan').innerHTML = h-12 + ":" + m + ":" + s;
}
var t = setTimeout(function(){time2()}, 0);
}
time3 = function() {
var today = new Date();
var h = today.getHours();
var m = today.getMinutes();
var s = today.getSeconds();
if (h>12) {
document.getElementById('hour_line').style.width = h-12 + 'em';
}
document.getElementById('minute_line').style.width = m + 'em';
document.getElementById('second_line').style.width = s + 'em';
var t = setTimeout(function(){time3()}, 0);
}
checkTime = function(i) {
if (i<10) {i = "0" + i}; // add zero in front of numbers < 10
return i;
}
</script>

JavaScript AM/PM time comparison

Suppose I have 2 datetime variables:
var fromdt = "2013/05/29 12:30 PM";
var todt = "2013/05/29 01:30 AM";
I want to compare these 2 datetimes. How can I get Javascript to recognize whether the time is AM or PM?
I think Javascript will compare the time in 24 hours format. Do I need to convert the time to 24 hour format? Is that correct? Could someone please suggest the correct solution....

Just use straight javascript functions
var fromdt = "2013/05/29 12:30 PM";
var todt = "2013/05/29 01:30 AM";
var from = new Date(Date.parse(fromdt));
var to = new Date(Date.parse(todt));
alert(from);
alert(to)
if (from > to) alert("From");
else alert("To");
Once the date is parsed into date form, you can do what you like with it. And you can compare dates using the standard operator signs ( >, < etc)
I'm not sure what you need to do with them, but http://www.w3schools.com/jsref/jsref_obj_date.asp is an okay reference.
And heres a crappy sandbox with the above code http://jsfiddle.net/QpFcW/
and a better one that XX deleted :( http://jsfiddle.net/QpFcW/1/

Use this function
function get_time() {
var time_t = "";
var d = new Date();
var cur_hour = d.getHours();
cur_hour < 12 ? (time_t = "am") : (time_t = "pm");
cur_hour == 0 ? (cur_hour = 12) : (cur_hour = cur_hour);
cur_hour > 12 ? (cur_hour = cur_hour - 12) : (cur_hour = cur_hour);
var curr_min = d.getMinutes().toString();
var curr_sec = d.getSeconds().toString();
if (curr_min.length == 1) {
curr_min = "0" + curr_min;
}
if (curr_sec.length == 1) {
curr_sec = "0" + curr_sec;
}
$("#updatedTime").html(
cur_hour + ":" + curr_min + ":" + curr_sec + " " + time_t
);
alert(cur_hour + ":" + curr_min + ":" + curr_sec + " " + time_t);
}

Javascript 12 Hour to 24 Format convertor

Is there any way i could convert a 12hour time format into a 24 hour format in JS?
I'm not that good with JavaScript at all so still surprised i could manage to get even this far.
What i'm trying to do is convert time from 12 hour to 24 hour so i can do comparison, like if endDate is greater than startDate, but what i cant understand is how to convert the 12 hour format i receive to a valid 24hour format.
$('#de_endTime').bind('blur', function()
{
sDate = $('#de_startDate').val();
startTime = $('#de_startTime').val();
endTime = $('#de_endTime').val();
if (startTime == ""){
alert("First input the start time");
$('#de_startTime').focus();
}
dSplit = sDate.split("-");
dYear = dSplit[0];
dMonth = dSplit[1] - 1;
dDay = dSplit[2];
stSplit = startTime.split(":");
stHour = stSplit[0];
stMin = stSplit[1].split(" ")[0];
stAmPm = stSplit[1].split(" ")[1];
etSplit = endTime.split(":");
etHour = etSplit[0];
etMin = etSplit[1].split(" ")[0];
etAmPm = etSplit[1].split(" ")[1];
fullStartDate = getDateObject(dYear, dMonth, dDay, stHour, stMin);
fullEndDate = getDateObject(dYear, dMonth, dDay, etHour, etMin);
if (fullStartDate - fullEndDate > 0){
alert("Start Time cannot be higher than End Time!");
}
});
Here is the getDateObject() function
function getDateObject(year, month, day, hours, minutes) {
var newDate = new Date();
newDate.setFullYear(year);
newDate.setMonth(month);
newDate.setDate(day);
newDate.setHours(hours);
newDate.setMinutes(minutes);
newDate.setSeconds(0);
newDate.setMilliseconds(0);
return newDate;
}
I'm not sure if i've provided enough detail, but please let me know if didnt :)
Thanks :)
[ EDIT ]
The new code, which seems to be outputting everything fine so far :)
$('#de_endTime').bind('blur', function()
{
sDate = $('#de_startDate').val();
startTime = $('#de_startTime').val();
endTime = $('#de_endTime').val();
if (startTime == ""){
alert("First input the start time");
$('#de_startTime').focus();
}
dSplit = sDate.split("-");
dYear = dSplit[0];
dMonth = dSplit[1];
dDay = dSplit[2];
fullIsoDate = dMonth + "/" + dDay + "/" + dYear;
//alert(fullIsoDate);
var fullStartDate = new Date(startTime + ' ' + fullIsoDate);
var fullEndDate = new Date(endTime + ' ' + fullIsoDate);
alert(fullStartDate);
if (fullStartDate - fullEndDate > 0){
alert("Start Time cannot be higher than End Time!");
}
alert(fullEndDate > fullStartDate)
});

date objects can be compared directly, and do not care about 12/24 hour format, so just put your times in two date objects and compare.
var dateOne = new Date('1:00 PM 1/1/1900');
var dateTwo = new Date('13:01 1/1/1900');
if(dateOne < dateTwo)
{
alert('DateOne is before DateTwo');
} else {
alert('DateOne is after DateTwo');
}
You will get a alert box that says DateOne is before DateTwo

I had been looking everywhere for just something SIMPLE to convert a time from 24-hour format to 12, or vice versa. Literally everything out there was only dealing with dates, or time and dates. So I made a simple time convertor and figured it anyone else needs one here it is (based off of the first example's split methods).
//usage timeConvert("12:01 PM","24") results 12:01:00
//OR timeConvert("12:01:00","12") results 12:01 PM
function timeConvert(time,twelvOrTwen){
var stSplit = time.split(":");
var stHour = stSplit[0];
var stMin = stSplit[1].split(" ")[0];
var stAmPm = stSplit[1].split(" ")[1];
var newhr = 0;
var ampm = '';
var newtime = '';
// alert("hour:"+stHour+"\nmin:"+stMin+"\nampm:"+stAmPm); //see current values
if (twelvOrTwen == "12") {
if (stHour == 12){
ampm = "PM";
newhr = 12;
}
else if (stHour == 00){;
ampm = "AM";
newmin = stMin;
newhr = 12;
}
else if (stHour > 12){
newhr = stHour - 12;
ampm = "PM";
}
else {
newhr = stHour;
ampm = "AM";
}
newtime = newhr+":"+stMin+" "+ampm;
}
else if (twelvOrTwen == "24"){
if ((stAmPm == "pm") || (stAmPm == "PM")){
if (stHour < 12) {
newhr = (stHour*1)+(1*12); //goes to 13
}
else { //means is 12:30 PM
newhr = 12;
}
}
newtime = newhr+":"+stMin+":"+"00";
}
else {
alert("No Time To Convert Or Didn't Specify 12 or 24");
}
return newtime;
}

Apparently, this question is already old, but I would be pasting my solution to answer the question that your title states. However this must mean that the 12 hour time format must come with a space separating the time and time of the day i.e. (am or pm).
Solution 1:
function convertTimeTo24(time) {
const realTime = time.split(" ");
if (realTime[1].toLowerCase() === "am") {
return realTime[0];
} else {
const timeToReturn = realTime[0].split(":");
const increaseHours = Number(timeToReturn[0]) + 12;
return `${increaseHours}:${timeToReturn[1]}`;
}
}

Converting 24 hour time to 12 hour time w/ AM & PM using Javascript

What is the best way to convert the following JSON returned value from a 24-hour format to 12-hour format w/ AM & PM? The date should stay the same - the time is the only thing that needs formatting.
February 04, 2011 19:00:00
P.S. Using jQuery if that makes it any easier! Would also prefer a simple function/code and not use Date.js.

This is how you can change hours without if statement:
hours = ((hours + 11) % 12 + 1);

UPDATE 2: without seconds option
UPDATE: AM after noon corrected, tested: http://jsfiddle.net/aorcsik/xbtjE/
I created this function to do this:
function formatDate(date) {
var d = new Date(date);
var hh = d.getHours();
var m = d.getMinutes();
var s = d.getSeconds();
var dd = "AM";
var h = hh;
if (h >= 12) {
h = hh - 12;
dd = "PM";
}
if (h == 0) {
h = 12;
}
m = m < 10 ? "0" + m : m;
s = s < 10 ? "0" + s : s;
/* if you want 2 digit hours:
h = h<10?"0"+h:h; */
var pattern = new RegExp("0?" + hh + ":" + m + ":" + s);
var replacement = h + ":" + m;
/* if you want to add seconds
replacement += ":"+s; */
replacement += " " + dd;
return date.replace(pattern, replacement);
}
alert(formatDate("February 04, 2011 12:00:00"));

//it is pm if hours from 12 onwards
suffix = (hours >= 12)? 'pm' : 'am';
//only -12 from hours if it is greater than 12 (if not back at mid night)
hours = (hours > 12)? hours -12 : hours;
//if 00 then it is 12 am
hours = (hours == '00')? 12 : hours;

For anyone reading who wants ONLY the time in the output, you can pass options to JavaScript's Date::toLocaleString() method. Example:
var date = new Date("February 04, 2011 19:00:00");
var options = {
hour: 'numeric',
minute: 'numeric',
hour12: true
};
var timeString = date.toLocaleString('en-US', options);
console.log(timeString);
timeString will be set to:
8:00 AM
Add "second: 'numeric'" to your options if you want seconds too. For all option see this.

Here's a reasonably terse way to do it using a Prototype:
Date.prototype.getFormattedTime = function () {
var hours = this.getHours() == 0 ? "12" : this.getHours() > 12 ? this.getHours() - 12 : this.getHours();
var minutes = (this.getMinutes() < 10 ? "0" : "") + this.getMinutes();
var ampm = this.getHours() < 12 ? "AM" : "PM";
var formattedTime = hours + ":" + minutes + " " + ampm;
return formattedTime;
}
Then all you have to do is convert your string value to a date and use the new method:
var stringValue = "February 04, 2011 19:00:00;
var dateValue = new Date(stringValue);
var formattedTime = dateValue.getFormattedTime();
Or in a single line:
var formattedTime = new Date("February 04, 2011 19:00:00").getFormattedTime();

Keep it simple and clean
var d = new Date();
var n = d.toLocaleString();
https://jsfiddle.net/rinu6200/3dkdxaad/#base

function pad(num) {return ("0" + num).slice(-2);}
function time1() {
var today = new Date(),
h = today.getHours(),
m = today.getMinutes(),
s = today.getSeconds();
h = h % 12;
h = h ? h : 12; // the hour '0' should be '12'
clk.innerHTML = h + ':' +
pad(m) + ':' +
pad(s) + ' ' +
(h >= 12 ? 'PM' : 'AM');
}
window.onload = function() {
var clk = document.getElementById('clk');
t = setInterval(time1, 500);
}
<span id="clk"></span>

jQuery doesn't have any Date utilities at all. If you don't use any additional libraries, the usual way is to create a JavaScript Date object and then extract the data from it and format it yourself.
For creating the Date object you can either make sure that your date string in the JSON is in a form that Date understands, which is IETF standard (which is basically RFC 822 section 5). So if you have the chance to change your JSON, that would be easiest. (EDIT: Your format may actually work the way it is.)
If you can't change your JSON, then you'll need to parse the string yourself and get day, mouth, year, hours, minutes and seconds as integers and create the Date object with that.
Once you have your Date object you'll need to extract the data you need and format it:
var myDate = new Date("4 Feb 2011, 19:00:00");
var hours = myDate.getHours();
var am = true;
if (hours > 12) {
am = false;
hours -= 12;
} else (hours == 12) {
am = false;
} else (hours == 0) {
hours = 12;
}
var minutes = myDate.getMinutes();
alert("It is " + hours + " " + (am ? "a.m." : "p.m.") + " and " + minutes + " minutes".);

1) "Squared" instructions for making 24-hours became 12-hours:
var hours24 = new Date().getHours(); // retrieve current hours (in 24 mode)
var dayMode = hours24 < 12 ? "am" : "pm"; // if it's less than 12 then "am"
var hours12 = hours24 <= 12 ? (hours24 == 0 ? 12 : hours24) : hours24 - 12;
// "0" in 24-mode now becames "12 am" in 12-mode – thanks to user #Cristian
document.write(hours12 + " " + dayMode); // printing out the result of code
2) In a single line (same result with slightly different algorythm):
var str12 = (h24 = new Date().getHours()) && (h24 - ((h24 == 0)? -12 : (h24 <= 12)? 0 : 12)) + (h24 < 12 ? " am" : " pm");
Both options return string, like "5 pm" or "10 am" etc.

You can take a look at this. One of the examples says:
var d = new Date(dateString);
Once you have Date object you can fairly easy play with it. You can either call toLocaleDateString, toLocaleTimeString or you can test if getHours is bigger than 12 and then just calculate AM/PM time.

date = date.replace(/[0-9]{1,2}(:[0-9]{2}){2}/, function (time) {
var hms = time.split(':'),
h = +hms[0],
suffix = (h < 12) ? 'am' : 'pm';
hms[0] = h % 12 || 12;
return hms.join(':') + suffix
});
edit: I forgot to deal with 12 o'clock am/pm. Fixed.

var dt = new Date();
var h = dt.getHours(), m = dt.getMinutes();
var thistime = (h > 12) ? (h-12 + ':' + m +' PM') : (h + ':' + m +' AM');
console.log(thistime);
Here is the Demo

function GetTime(date) {
var currentTime = (new Date(date))
var hours = currentTime.getHours()
//Note: before converting into 12 hour format
var suffix = '';
if (hours > 11) {
suffix += "PM";
} else {
suffix += "AM";
}
var minutes = currentTime.getMinutes()
if (minutes < 10) {
minutes = "0" + minutes
}
if (hours > 12) {
hours -= 12;
} else if (hours === 0) {
hours = 12;
}
var time = hours + ":" + minutes + " " + suffix;
return time;
}

Please try with below code
var s = "15 Feb 2015 11.30 a.m";
var times = s.match("((([0-9])|([0-2][0-9])).([0-9][0-9])[\t ]?((a.m|p.m)|(A.M|P.M)))");
var time = "";
if(times != null){
var hour = times[2];
if((times[6] == "p.m" || times[6] == "P.M")){
if(hour < 12){
hour = parseInt(hour) + parseInt(12);
}else if(hour == 12){
hour = "00";
}
}
time = [hour, times[5], "00"].join(":");
}
Thanks

This worked for me!
function main() {
var time = readLine();
var formattedTime = time.replace('AM', ' AM').replace('PM', ' PM');
var separators = [':', ' M'];
var hms = formattedTime.split(new RegExp('[' + separators.join('') + ']'));
if (parseInt(hms[0]) < 12 && hms[3] == 'P')
hms[0] = parseInt(hms[0]) + 12;
else if (parseInt(hms[0]) == 12 && hms[3] == 'A')
hms[0] = '00';
console.log(hms[0] + ':' + hms[1] + ':' + hms[2]);
}

You could try this more generic function:
function to12HourFormat(date = (new Date)) {
return {
hours: ((date.getHours() + 11) % 12 + 1),
minutes: date.getMinutes(),
meridian: (date.getHours() >= 12) ? 'PM' : 'AM',
};
}
Returns a flexible object format.
https://jsbin.com/vexejanovo/edit

I'm a relative newbie, but here's what I came up with for one of my own projects, and it seems to work. There may be simpler ways to do it.
function getTime() {
var nowTimeDate = new Date();
var nowHour = nowTimeDate.getHours();
var nowMinutes = nowTimeDate.getMinutes();
var suffix = nowHour >= 12 ? "pm" : "am";
nowHour = (suffix == "pm" & (nowHour > 12 & nowHour < 24)) ? (nowHour - 12) : nowHour;
nowHour = nowHour == 0 ? 12 : nowHour;
nowMinutes = nowMinutes < 10 ? "0" + nowMinutes : nowMinutes;
var currentTime = nowHour + ":" + nowMinutes + suffix;
document.getElementById("currentTime").innerHTML = currentTime;
}

this is your html code where you are calling function to convert 24 hour time format to 12 hour with am/pm
<pre id="tests" onClick="tConvert('18:00:00')">
test on click 18:00:00
</pre>
<span id="rzlt"></span>
now in js code write this tConvert function as it is
function tConvert (time)
{
// Check correct time format and split into components
time = time.toString ().match (/^([01]\d|2[0-3])(:)([0-5]\d)(:[0-5]\d)?$/) || [time];
if (time.length > 1)
{ // If time format correct
time = time.slice (1); // Remove full string match value
time[5] = +time[0] < 12 ? 'AM' : 'PM'; // Set AM/PM
time[0] = +time[0] % 12 || 12; // Adjust hours
}
//return time; // return adjusted time or original string
var tel = document.getElementById ('rzlt');
tel.innerHTML= time.join ('');
}
converting 18:00:00 to 6:00:00PM working for me

This function will convert in both directions:
12 to 24 hour or 24 to 12 hour
function toggle24hr(time, onoff){
if(onoff==undefined) onoff = isNaN(time.replace(':',''))//auto-detect format
var pm = time.toString().toLowerCase().indexOf('pm')>-1 //check if 'pm' exists in the time string
time = time.toString().toLowerCase().replace(/[ap]m/,'').split(':') //convert time to an array of numbers
time[0] = Number(time[0])
if(onoff){//convert to 24 hour:
if((pm && time[0]!=12)) time[0] += 12
else if(!pm && time[0]==12) time[0] = '00' //handle midnight
if(String(time[0]).length==1) time[0] = '0'+time[0] //add leading zeros if needed
}else{ //convert to 12 hour:
pm = time[0]>=12
if(!time[0]) time[0]=12 //handle midnight
else if(pm && time[0]!=12) time[0] -= 12
}
return onoff ? time.join(':') : time.join(':')+(pm ? 'pm' : 'am')
}
Here's some examples:
//convert to 24 hour:
toggle24hr('12:00am') //returns 00:00
toggle24hr('2:00pm') //returns 14:00
toggle24hr('8:00am') //returns 08:00
toggle24hr('12:00pm') //returns 12:00
//convert to 12 hour:
toggle24hr('14:00') //returns 2:00pm
toggle24hr('08:00') //returns 8:00am
toggle24hr('12:00') //returns 12:00pm
toggle24hr('00:00') //returns 12:00am
//you can also force a specific format like this:
toggle24hr('14:00',1) //returns 14:00
toggle24hr('14:00',0) //returns 2:00pm

Here you go
var myDate = new Date("February 04, 2011 19:00:00");
var hr = myDate.getHours();
var convHrs = "";
var ampmSwitch = "";
ampmSwitch = (hr > 12)? "PM":"AM";
convHrs = (hr >12)? hr-12:hr;
// Build back the Date / time using getMonth/ getFullYear and getDate and other functions on the myDate object. Enclose it inside a func and there you got the working 12 hrs converter ;)
And here's the converter func for yas ;) Happy coding!!
function convertTo12Hrs(yourDateTime){
var myDate = new Date(yourDateTime);
var dtObject = new Object();
var monthsCollection = {0:"January", 1:"February",2:"March",3:"April",4:"May",5:"June",6:"July",7:"August",8:"September",9:"October",10:"November",11:"December"};
dtObject.year = myDate.getFullYear();
dtObject.month = monthsCollection[myDate.getMonth()];
dtObject.day = (myDate.getDate()<10)?"0"+myDate.getDate():myDate.getDate();
dtObject.minutes = (myDate.getMinutes() < 10)? "0"+myDate.getMinutes():myDate.getMinutes();
dtObject.seconds = (myDate.getSeconds() < 10)? "0"+myDate.getSeconds():myDate.getSeconds();
// Check if hours are greater than 12? Its PM
dtObject.ampmSwitch = (myDate.getHours() > 12)? "PM":"AM";
// Convert the hours
dtObject.hour = (myDate.getHours() > 12)?myDate.getHours()-12:myDate.getHours();
// Add the 0 as prefix if its less than 10
dtObject.hour = (dtObject.hour < 10)? "0"+dtObject.hour:dtObject.hour;
// Format back the string as it was or return the dtObject object or however you like. I am returning the object here
return dtObject;
}
invoke it like
convertTo12Hrs("February 04, 2011 19:00:00"); it will return you the object, which in turn you can use to format back your datetime string as you fancy...

You're going to end up doing alot of string manipulation anyway,
so why not just manipulate the date string itself?
Browsers format the date string differently.
Netscape ::: Fri May 11 2012 20:15:49 GMT-0600 (Mountain Daylight Time)
IE ::: Fri May 11 20:17:33 MDT 2012
so you'll have to check for that.
var D = new Date().toString().split(' ')[(document.all)?3:4];
That will set D equal to the 24-hour HH:MM:SS string. Split that on the
colons, and the first element will be the hours.
var H = new Date().toString().split(' ')[(document.all)?3:4].split(':')[0];
You can convert 24-hour hours into 12-hour hours, but that hasn't
actually been mentioned here. Probably because it's fairly CRAZY
what you're actually doing mathematically when you convert hours
from clocks. In fact, what you're doing is adding 23, mod'ing that
by 12, and adding 1
twelveHour = ((twentyfourHour+23)%12)+1;
So, for example, you could grab the whole time from the date string, mod
the hours, and display all that with the new hours.
var T = new Date().toString().split(' ')[(document.all)?3:4].split(':');
T[0] = (((T[0])+23)%12)+1;
alert(T.join(':'));
With some smart regex, you can probably pull the hours off the HH:MM:SS
part of the date string, and mod them all in the same line. It would be
a ridiculous line because the backreference $1 couldn't be used in
calculations without putting a function in the replace.
Here's how that would look:
var T = new Date().toString().split(' ')[(document.all)?3:4].replace(/(^\d\d)/,function(){return ((parseInt(RegExp.$1)+23)%12)+1} );
Which, as I say, is ridiculous. If you're using a library that CAN perform
calculations on backreferences, the line becomes:
var T = new Date().toString().split(' ')[(document.all)?3:4].replace(/(^\d\d)/, (($1+23)%12)+1);
And that's not actually out of the question as useable code, if you document it well.
That line says:
Make a Date string, break it up on the spaces, get the browser-apropos part,
and replace the first two-digit-number with that number mod'ed.
Point of the story is, the way to convert 24-hour-clock hours to 12-hour-clock hours
is a non-obvious mathematical calculation:
You add 23, mod by 12, then add one more.

Here is a nice little function that worked for me.
function getDisplayDatetime() {
var d = new Date(); var hh = d.getHours(); var mm = d.getMinutes(); var dd = "AM"; var h = hh;
if (mm.toString().length == 1) {
mm = "0" + mm;
}
if (h >= 12) {
h = hh - 12;
dd = "PM";
}
if (h == 0) {
h = 12;
}
var Datetime = "Datetime: " + d.getFullYear() + "/" + (d.getMonth() + 1) + "/" + d.getUTCDate() + " " + h + ":" + mm;
return Datetime + " " + dd;
}

I noticed there is already an answer, but I wanted to share my own solution, using pure JavaScript:
function curTime(pm) {
var dt = new Date();
var hr = dt.getHours(), min = dt.getMinutes(), sec = dt.getSeconds();
var time = (pm ? ((hr+11)%12+1) : (hr<10?'0':'')+hr)+":"+(min<10?'0':'')+min+":"+(sec<10?'0':'')+sec+(pm ? (hr>12 ? " PM" : " AM") : "");
return time;
}
You can see it in action at https://jsfiddle.net/j2xk312m/3/ using the following code block:
(function() {
function curTime(pm) {
var dt = new Date();
var hr = dt.getHours(), min = dt.getMinutes(), sec = dt.getSeconds();
var time = (pm ? ((hr+11)%12+1) : (hr<10?'0':'')+hr)+":"+(min<10?'0':'')+min+":"+(sec<10?'0':'')+sec+(pm ? (hr>12 ? " PM" : " AM") : "");
return time;
}
alert("12-hour Format: "+curTime(true)+"\n24-hour Format: "+curTime(false));
})();

This way you have more control over the output - i.e - if you wanted the time format to be '4:30 pm' instead of '04:30 P.M.' - you can convert to whatever format you decide you want - and change it later too. Instead of being constrained to some old method that does not allow any flexibility.
and you only need to convert the first 2 digits as the minute and seconds digits are the same in 24 hour time or 12 hour time.
var my_time_conversion_arr = {'01':"01", '02':"02", '03':"03", '04':"04", '05':"05", '06':"06", '07':"07", '08':"08", '09':"09", '10':"10", '11':"11", '12': "12", '13': "1", '14': "2", '15': "3", '16': "4", '17': "5", '18': "6", '19': "7", '20': "8", '21': "9", '22': "10", '23': "11", '00':"12"};
var AM_or_PM = "";
var twenty_four_hour_time = "16:30";
var twenty_four_hour_time_arr = twenty_four_hour_time.split(":");
var twenty_four_hour_time_first_two_digits = twenty_four_hour_time_arr[0];
var first_two_twelve_hour_digits_converted = my_time_conversion_arr[twenty_four_hour_time_first_two_digits];
var time_strng_to_nmbr = parseInt(twenty_four_hour_time_first_two_digits);
if(time_strng_to_nmbr >12){
//alert("GREATER THAN 12");
AM_or_PM = "pm";
}else{
AM_or_PM = "am";
}
var twelve_hour_time_conversion = first_two_twelve_hour_digits_converted+":"+twenty_four_hour_time_arr[1]+" "+AM_or_PM;