How do I combine these variables in my code :
var date1 = "13:38";
var date2 = "2019-05-14T00:00:00"
I want to add the time from date1 to date2, so the result should be "2019-05-14T13:38:00"
It's not clear what you are trying to do. If the date and time timestamp always has a time of 00:00:00 and you just want to update the time component, you can do that as a string.
Since "2019-05-14T00:00:00" has no offset, it should be parsed as local, so will represent a different moment in time for each different location with a different offset. If it should be parsed as UTC, please make that clear in the OP. It's fairly easy to go either way, you just have to make it clear how it should be treated.
I've allowed for an optional seconds component.
var date1 = "13:38";
var date2 = "2019-05-14T00:00:00";
let [h, m, s] = date1.split(':');
console.log(date2.substring(0,11) + h + ':' + m + ':' + (s||'00'));
However, if the date and time timestamp also has a non–zero time component and you need to add time, a Date object can make life easier:
// Parse ISO 8601 timestamp in YYYY-MM-DDTHH:mm:ss format
// Assumes no offset, parses as local
function parseDateTime(dt) {
let [Y, M, D, h, m, s] = dt.split(/\D/);
return new Date(Y, M-1, D, h, m, s);
}
// Add time in hh:mm[:ss] format to a date
// Returns a new date, doesn't modify date passed in
function addTime(date, time) {
let [h, m, s] = time.split(/\D/);
let d = new Date(+date);
d.setHours(d.getHours() + +h,
d.getMinutes() + +m,
d.getSeconds() + +m);
return d;
}
let date1 = "13:38";
let date2 = "2019-05-14T03:42:28";
let d = parseDateTime(date2);
let e = addTime(d, date1);
// UTC timestamp in ISO 8601 format
console.log(e.toISOString());
Note that in the second example, the displayed value uses the built–in toISOString method that shifts the offset to UTC (+0). If you want the ISO format but in the local timezone, then you can manually format the string. There are lots of questions and answers on how to do that.
There are also numerous libraries that can help. Since the Date object hasn't changed much in over 20 years, any that have been around a while should be OK.
You will have to parse the first timesting and construct a new date object from it. You should construct a UTC object and pass that into the constructor.
For the second datestring, you will need to add the Zulu token to the end to donate a UTC time and make it ISO 8601 compliant.
After you have your two date objects, update the minutes and hours of the second date object, because that one already stores date information.
const date1 = "13:38";
const date2 = "2019-05-14T00:00:00";
const dateObj1 = (tokens =>
new Date(Date.UTC(0, 0, 0, tokens[0], tokens[1])))
(date1.split(':'));
const dateObj2 = new Date(date2 + 'Z');
dateObj2.setUTCMinutes(dateObj2.getUTCMinutes() + dateObj1.getUTCMinutes());
dateObj2.setUTCHours(dateObj2.getUTCHours() + dateObj1.getUTCHours());
console.log(dateObj2.toISOString().substring(0, 19)); // 2019-05-14T13:38:00
If you want to do this in Moment, you can try the following:
const date1 = "13:38";
const date2 = "2019-05-14T00:00:00";
const moment1 = moment.utc(date1, 'HH:mm');
const moment2 = moment.utc(date2)
.add(moment1.minutes(), 'minutes')
.add(moment1.hours(), 'hours')
console.log(moment2.format('YYYY-MM-DDTHH:mm:ss'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.27.0/moment.min.js"></script>
I have two variables, date & time...
var date = "2012-12-05";
var time = "18:00";
How can I format this into a UTC formatted date. This is so I can use it within the Facebook API..
Facebook states I need it in this format:
Precise-time (e.g., '2012-07-04T19:00:00-0700'): events that start at a particular point in time, in a specific offset from UTC. This is the way new Facebook events keep track of time, and allows users to view events in different timezones.
Any help would be much appreciated.. Thanks!
This format is called ISO 8601
Do you know what timezone you are in? If you do, you can do like this:
var datetime = date + 'T' + time + ":00+0000';
if the timezone is +0.
if not, then:
var d = new Date()
var n = d.getTimezoneOffset();
var timeZone = Math.floor( Math.abs( n/60 ) );
var timeZoneString = (d.getTimezoneOffset() < 0 ? '-' : '+' ) + ( timeZone < 10 ? '0' + timeZone : timeZone ) + '00';
var datetime = date + 'T' + time + ':00' + timeZoneString;
Here is a fiddle: http://jsfiddle.net/ajySr/
Try the following:
var date = new Date(2012, 12, 5, 18, 0, 0, 0);
var date_utc = new Date(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate(), date.getUTCHours(), date.getUTCMinutes(), date.getUTCSeconds());
The Date function can be used the following ways:
var d = new Date();
var d = new Date(milliseconds);
var d = new Date(dateString);
var d = new Date(year, month, day, hours, minutes, seconds, milliseconds);
This was taken from a related post here: How do you convert a JavaScript date to UTC?
To find out more, please refer to: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date
What is the best way to calculate the time passed since (last) midnight in ms?
Create a new date using the current day/month/year, and get the difference.
var now = new Date(),
then = new Date(
now.getFullYear(),
now.getMonth(),
now.getDate(),
0,0,0),
diff = now.getTime() - then.getTime(); // difference in milliseconds
A bunch of answers so here another:
var d = new Date(), e = new Date(d);
var msSinceMidnight = e - d.setHours(0,0,0,0);
As a function:
function getMsSinceMidnight(d) {
var e = new Date(d);
return d - e.setHours(0,0,0,0);
}
alert(getMsSinceMidnight(new Date()));
Many answers except RobG's (recommended answer), Kolink's and Lai's are wrong here
Let's look closer together
First mistake
OptimusCrime and Andrew D. answers:
As Mala sugested, if the daylight saving correction was applied the nearest midnight, we get incorrect value. Let's debug:
Suppose it's last Sunday of March
The time is fixed at 2 am.
If we see 10 am on the clock, there's actually 11 hours passed from midnight
But instead we count 10 * 60 * 60 * 1000 ms
The trick is played when midnight happens in different DST state then current
Second mistake
kennebeck's answer:
As RobG wrote, the clock can tick if you get the system time twice. We can even appear in different dates sometimes. You can reproduce this in a loop:
for (var i = 0; true; i++) {
if ((new Date()).getTime() - (new Date()).getTime()) {
alert(i); // console.log(i); // for me it's about a 1000
break;
}
}
Third is my personal pitfall you could possibly experience
Consider the following code:
var d = new Date(),
msSinceMidnight = d - d.setHours(0,0,0,0);
msSinceMidnight is always 0 as the object is changed during computation before the substraction operation
At last, this code works:
var d = new Date(),
msSinceMidnight = d.getTime() - d.setHours(0,0,0,0);
Simpler to write, if you don't mind creating two dates.
var msSinceMidnight= new Date()-new Date().setHours(0,0,0,0);
var d=new Date();
// offset from midnight in Greenwich timezone
var msFromMidnightInGMT=d%86400000;
// offset from midnight in locale timezone
var msFromMidnightLocale=(d.getTime()-d.getTimezoneOffset()*60000)%86400000;
var today = new Date();
var d = new Date(today.getFullYear(), today.getMonth(), today.getDate(), 0, 0, 0, 0);
var difference = today.getTime() - d.getTime();
Seconds since midnight would simply be to display the time, but instead of using hours:minutes:seconds, everything is converted into seconds.
I think this should do it:
var now = new Date();
var hours = now.getHours()*(60*60);
var minutes = now.getMinutes()*60;
var seconds = now.getSeconds();
var secSinceMidnight = hours+minutes+seconds;
Want to improve this post? Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted.
Is there an easy way of taking a olain JavaScript Date (e.g. today) and going back X days?
So, for example, if I want to calculate the date 5 days before today.
Try something like this:
var d = new Date();
d.setDate(d.getDate()-5);
Note that this modifies the date object and returns the time value of the updated date.
var d = new Date();
document.write('Today is: ' + d.toLocaleString());
d.setDate(d.getDate() - 5);
document.write('<br>5 days ago was: ' + d.toLocaleString());
var dateOffset = (24*60*60*1000) * 5; //5 days
var myDate = new Date();
myDate.setTime(myDate.getTime() - dateOffset);
If you're performing lots of headachy date manipulation throughout your web application, DateJS will make your life much easier:
http://simonwillison.net/2007/Dec/3/datejs/
It goes something like this:
var d = new Date(); // today!
var x = 5; // go back 5 days!
d.setDate(d.getDate() - x);
I noticed that the getDays+ X doesn't work over day/month boundaries. Using getTime works as long as your date is not before 1970.
var todayDate = new Date(), weekDate = new Date();
weekDate.setTime(todayDate.getTime()-(7*24*3600000));
If you want it all on one line instead.
5 days from today
//past
var fiveDaysAgo = new Date(new Date().setDate(new Date().getDate() - 5));
//future
var fiveDaysInTheFuture = new Date(new Date().setDate(new Date().getDate() + 5));
5 days from a specific date
var pastDate = new Date('2019-12-12T00:00:00');
//past
var fiveDaysAgo = new Date(new Date().setDate(pastDate.getDate() - 5));
//future
var fiveDaysInTheFuture = new Date(new Date().setDate(pastDate.getDate() + 5));
I wrote a function you can use.
function AddOrSubractDays(startingDate, number, add) {
if (add) {
return new Date(new Date().setDate(startingDate.getDate() + number));
} else {
return new Date(new Date().setDate(startingDate.getDate() - number));
}
}
console.log('Today : ' + new Date());
console.log('Future : ' + AddOrSubractDays(new Date(), 5, true));
console.log('Past : ' + AddOrSubractDays(new Date(), 5, false));
I find a problem with the getDate()/setDate() method is that it too easily turns everything into milliseconds, and the syntax is sometimes hard for me to follow.
Instead I like to work off the fact that 1 day = 86,400,000 milliseconds.
So, for your particular question:
today = new Date()
days = 86400000 //number of milliseconds in a day
fiveDaysAgo = new Date(today - (5*days))
Works like a charm.
I use this method all the time for doing rolling 30/60/365 day calculations.
You can easily extrapolate this to create units of time for months, years, etc.
get moment.js. All the cool kids use it. It has more formatting options, etc. Where
var n = 5;
var dateMnsFive = moment(<your date>).subtract(n , 'day');
Optional! Convert to JS Date obj for Angular binding.
var date = new Date(dateMnsFive.toISOString());
Optional! Format
var date = dateMnsFive.format("YYYY-MM-DD");
A few of the existing solutions were close, but not quite exactly what I wanted. This function works with both positive or negative values and handles boundary cases.
function addDays(date, days) {
return new Date(
date.getFullYear(),
date.getMonth(),
date.getDate() + days,
date.getHours(),
date.getMinutes(),
date.getSeconds(),
date.getMilliseconds()
);
}
Without using the second variable, you can replace 7 for with your back x days:
let d=new Date(new Date().getTime() - (7 * 24 * 60 * 60 * 1000))
I made this prototype for Date so that I could pass negative values to subtract days and positive values to add days.
if(!Date.prototype.adjustDate){
Date.prototype.adjustDate = function(days){
var date;
days = days || 0;
if(days === 0){
date = new Date( this.getTime() );
} else if(days > 0) {
date = new Date( this.getTime() );
date.setDate(date.getDate() + days);
} else {
date = new Date(
this.getFullYear(),
this.getMonth(),
this.getDate() - Math.abs(days),
this.getHours(),
this.getMinutes(),
this.getSeconds(),
this.getMilliseconds()
);
}
this.setTime(date.getTime());
return this;
};
}
So, to use it i can simply write:
var date_subtract = new Date().adjustDate(-4),
date_add = new Date().adjustDate(4);
I like doing the maths in milliseconds. So use Date.now()
var newDate = Date.now() + -5*24*3600*1000; // date 5 days ago in milliseconds
and if you like it formatted
new Date(newDate).toString(); // or .toUTCString or .toISOString ...
NOTE: Date.now() doesn't work in older browsers (eg IE8 I think). Polyfill here.
UPDATE June 2015
#socketpair pointed out my sloppiness. As s/he says "Some day in year have 23 hours, and some 25 due to timezone rules".
To expand on that, the answer above will have daylightsaving inaccuracies in the case where you want to calculate the LOCAL day 5 days ago in a timezone with daylightsaving changes and you
assume (wrongly) that Date.now() gives you the current LOCAL now time, or
use .toString() which returns the local date and therefore is incompatible with the Date.now() base date in UTC.
However, it works if you're doing your math all in UTC, eg
A. You want the UTC date 5 days ago from NOW (UTC)
var newDate = Date.now() + -5*24*3600*1000; // date 5 days ago in milliseconds UTC
new Date(newDate).toUTCString(); // or .toISOString(), BUT NOT toString
B. You start with a UTC base date other than "now", using Date.UTC()
newDate = new Date(Date.UTC(2015, 3, 1)).getTime() + -5*24*3600000;
new Date(newDate).toUTCString(); // or .toISOString BUT NOT toString
split your date into parts, then return a new Date with the adjusted values
function DateAdd(date, type, amount){
var y = date.getFullYear(),
m = date.getMonth(),
d = date.getDate();
if(type === 'y'){
y += amount;
};
if(type === 'm'){
m += amount;
};
if(type === 'd'){
d += amount;
};
return new Date(y, m, d);
}
Remember that the months are zero based, but the days are not. ie new Date(2009, 1, 1) == 01 February 2009, new Date(2009, 1, 0) == 31 January 2009;
Some people suggested using moment.js to make your life easier when handling dates in js. Time has passed since those answers and it is noteworthy, that the authors of moment.js now discourage its use. Mainly due to its size and lack of tree-shaking-support.
If you want to go the library route, use an alternative like Luxon. It is significantly smaller (because of its clever use of the Intl object and support for tree-shaking) and just as versatile as moment.js.
To go back 5 days from today in Luxon, you would do:
import { DateTime } from 'luxon'
DateTime.now().minus({ days: 5 });
function addDays (date, daysToAdd) {
var _24HoursInMilliseconds = 86400000;
return new Date(date.getTime() + daysToAdd * _24HoursInMilliseconds);
};
var now = new Date();
var yesterday = addDays(now, - 1);
var tomorrow = addDays(now, 1);
See the following code, subtract the days from the current date. Also, set the month according to substracted date.
var today = new Date();
var substract_no_of_days = 25;
today.setTime(today.getTime() - substract_no_of_days* 24 * 60 * 60 * 1000);
var substracted_date = (today.getMonth()+1) + "/" +today.getDate() + "/" + today.getFullYear();
alert(substracted_date);
I have created a function for date manipulation. you can add or subtract any number of days, hours, minutes.
function dateManipulation(date, days, hrs, mins, operator) {
date = new Date(date);
if (operator == "-") {
var durationInMs = (((24 * days) * 60) + (hrs * 60) + mins) * 60000;
var newDate = new Date(date.getTime() - durationInMs);
} else {
var durationInMs = (((24 * days) * 60) + (hrs * 60) + mins) * 60000;
var newDate = new Date(date.getTime() + durationInMs);
}
return newDate;
}
Now, call this function by passing parameters. For example, here is a function call for getting date before 3 days from today.
var today = new Date();
var newDate = dateManipulation(today, 3, 0, 0, "-");
Use MomentJS.
function getXDaysBeforeDate(referenceDate, x) {
return moment(referenceDate).subtract(x , 'day').format('MMMM Do YYYY, h:mm:ss a');
}
var yourDate = new Date(); // let's say today
var valueOfX = 7; // let's say 7 days before
console.log(getXDaysBeforeDate(yourDate, valueOfX));
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.22.2/moment.min.js"></script>
The top answers led to a bug in my code where on the first of the month it would set a future date in the current month. Here is what I did,
curDate = new Date(); // Took current date as an example
prvDate = new Date(0); // Date set to epoch 0
prvDate.setUTCMilliseconds((curDate - (5 * 24 * 60 * 60 * 1000))); //Set epoch time
I like the following because it is one line. Not perfect with DST changes but usually good enough for my needs.
var fiveDaysAgo = new Date(new Date() - (1000*60*60*24*5));
Using Modern JavaScript function syntax
const getDaysPastDate = (daysBefore, date = new Date) => new Date(date - (1000 * 60 * 60 * 24 * daysBefore));
console.log(getDaysPastDate(1)); // yesterday
A easy way to manage dates is use Moment.js
You can use add. Example
var startdate = "20.03.2014";
var new_date = moment(startdate, "DD.MM.YYYY");
new_date.add(5, 'days'); //Add 5 days to start date
alert(new_date);
Docs http://momentjs.com/docs/#/manipulating/add/
for me all the combinations worked fine with below code snipplet ,
the snippet is for Angular-2 implementation ,
if you need to add days , pass positive numberofDays , if you need to substract pass negative numberofDays
function addSubstractDays(date: Date, numberofDays: number): Date {
let d = new Date(date);
return new Date(
d.getFullYear(),
d.getMonth(),
(d.getDate() + numberofDays)
);
}
I get good mileage out of date.js:
http://www.datejs.com/
d = new Date();
d.add(-10).days(); // subtract 10 days
Nice!
Website includes this beauty:
Datejs doesn’t just parse strings, it slices them cleanly in two
If you want to both subtract a number of days and format your date in a human readable format, you should consider creating a custom DateHelper object that looks something like this :
var DateHelper = {
addDays : function(aDate, numberOfDays) {
aDate.setDate(aDate.getDate() + numberOfDays); // Add numberOfDays
return aDate; // Return the date
},
format : function format(date) {
return [
("0" + date.getDate()).slice(-2), // Get day and pad it with zeroes
("0" + (date.getMonth()+1)).slice(-2), // Get month and pad it with zeroes
date.getFullYear() // Get full year
].join('/'); // Glue the pieces together
}
}
// With this helper, you can now just use one line of readable code to :
// ---------------------------------------------------------------------
// 1. Get the current date
// 2. Subtract 5 days
// 3. Format it
// 4. Output it
// ---------------------------------------------------------------------
document.body.innerHTML = DateHelper.format(DateHelper.addDays(new Date(), -5));
(see also this Fiddle)
To calculate relative time stamps with a more precise difference than whole days, you can use Date.getTime() and Date.setTime() to work with integers representing the number of milliseconds since a certain epoch—namely, January 1, 1970. For example, if you want to know when it’s 17 hours after right now:
const msSinceEpoch = (new Date()).getTime();
const fortyEightHoursLater = new Date(msSinceEpoch + 48 * 60 * 60 * 1000).toLocaleString();
const fortyEightHoursEarlier = new Date(msSinceEpoch - 48 * 60 * 60 * 1000).toLocaleString();
const fiveDaysAgo = new Date(msSinceEpoch - 120 * 60 * 60 * 1000).toLocaleString();
console.log({msSinceEpoch, fortyEightHoursLater, fortyEightHoursEarlier, fiveDaysAgo})
reference
function daysSinceGivenDate (date) {
const dateInSeconds = Math.floor((new Date().valueOf() - date.valueOf()) / 1000);
const oneDayInSeconds = 86400;
return Math.floor(dateInSeconds / oneDayInSeconds); // casted to int
};
console.log(daysSinceGivenDate(new Date())); // 0
console.log(daysSinceGivenDate(new Date("January 1, 2022 03:24:00"))); // relative...
First arg is the date to start with and second is how mush day you want to increase or reduce to the date
example (1)- pass -1 to reduce date by one day
example (2)- pass 1 to increase date by one day
const EditDay = (date: Date, num: number): Date => {
return new Date(date.getTime() + num * 24 * 60 * 60 * 1000)
}
When setting the date, the date converts to milliseconds, so you need to convert it back to a date:
This method also take into consideration, new year change etc.
function addDays( date, days ) {
var dateInMs = date.setDate(date.getDate() - days);
return new Date(dateInMs);
}
var date_from = new Date();
var date_to = addDays( new Date(), parseInt(days) );
You can using Javascript.
var CurrDate = new Date(); // Current Date
var numberOfDays = 5;
var days = CurrDate.setDate(CurrDate.getDate() + numberOfDays);
alert(days); // It will print 5 days before today
For PHP,
$date = date('Y-m-d', strtotime("-5 days")); // it shows 5 days before today.
echo $date;
Hope it will help you.
I converted into millisecond and deducted days else month and year won't change and logical
var numberOfDays = 10;//number of days need to deducted or added
var date = "01-01-2018"// date need to change
var dt = new Date(parseInt(date.substring(6), 10), // Year
parseInt(date.substring(3,5), 10) - 1, // Month (0-11)
parseInt(date.substring(0,2), 10));
var new_dt = dt.setMilliseconds(dt.getMilliseconds() - numberOfDays*24*60*60*1000);
new_dt = new Date(new_dt);
var changed_date = new_dt.getDate()+"-"+(new_dt.getMonth()+1)+"-"+new_dt.getFullYear();
Hope helps