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Convert a string in date (so formatted: month day, year hh:mm:ss)

I know there are tons of questions about date formatting, but I'm stuck with a conversion.
I have a string so formatted: mag 11, 2021 2:31:00 pm ("mag" is the abbreviation of May in italian).
I want to convert it in date so I can change it to the format DD/MM/YYYY HH:MM:ss (in this case "11/05/2021 14:31").
I tried to use the new Date or Date.parse functions, but in console it returns me the error 'Invalid date'.
Here's what I tried:
let a = "mag 11, 2021 2:31:00 pm";
let b = new Date(a);
console.log(b);
console output -----> Invalid Date
let a = "mag 11, 2021 2:31:00 pm";
let b = Date.parse(a);
console.log(b);
console output -----> NaN
Any idea? Thx

This question has been answered many times before, the following is for this specific case.
A Date object isn't required, the timestamp can be split into its parts, the month name converted to a number then the parts reformatted, e.g.
/*
mag 11, 2021 2:31:00 pm => DD/MM/YYYY HH:MM:ss
e.g. 11/05/2021 14:31
*/
function reformatDate(date) {
let z = n => ('0'+n).slice(-2);
let months = [,'gen','feb','mar','apr','mag','giu',
'lug','ago','set','ott','nov','dic'];
let [M,D,Y,h,m,s,ap] = date.toLowerCase().split(/\W+/);
h = h%12 + (ap == 'am'? 0 : 12);
M = months.indexOf(M);
return `${z(D)}/${z(M)}/${Y} ${z(h)}:${m}`;
}
console.log(reformatDate('mag 11, 2021 2:31:00 pm'));
In the OP, the format tokens include seconds but the example doesn't. Adding seconds to the above output if required should be easy.
The above can be modified to build the month names array based on a specific language, but then language to use would need to be passed to the function too.
If a library is used to parse the string, the language and format must be specified for the parser (e.g. date-fns allows setting the parse and format language), then the language and format of the output. So unless other date manipulation is required, a library may be more trouble than it's worth.

let now = new Date();
var dateString = moment(now).format('YYYY-MM-DD');
console.log(dateString) // Output: 2020-07-21
var dateStringWithTime = moment(now).format('YYYY-MM-DD HH:MM:SS');
console.log(dateStringWithTime) // Output: 2020-07-21 07:24:06
You can check here for all details of dateTime for Javascript

Format existing date variable with moment.js

I have a date variable (coming from an external source):
var date = '28/04/2017';
var time = '19:28';
It is possible to format these variables with moment.js (or without?) to variout formats?
Example: 04.28 19:28, 2017.04.28 19:28 or even Today at 19:28 (with moment().calendar();)
I tried
moment(date+' '+time).format('MM.DD.YYYY');
...but I am getting "Invalid date" error.

You're using moment(String) method, but you're not passing a Supported
format that it expects to parse.
You should use moment(String, String), where the first String is the input date string, and second is the format of your input date String.
Try this:
moment(date+' '+time,'DD/MM/YYYY HH:mm').format('MM.DD.YYYY');

Try:
moment(new Date(date + ' ' + time)).format('MM.DD.YYYY');

You need to keep the same format:
var date = '04-28-2017'; // Month/day/year
var time = '19:28';
console.log( moment(date, 'MM-DD-YYYY').format('MMMM D') ) // April 28

Convert date to UTC using moment.js

Probably and easy answer to this but I can't seem to find a way to get moment.js to return a UTC date time in milliseconds. Here is what I am doing:
var date = $("#txt-date").val(),
expires = moment.utc(date);
Any idea what I am doing wrong?

This is found in the documentation. With a library like moment, I urge you to read the entirety of the documentation. It's really important.
Assuming the input text is entered in terms of the users's local time:
var expires = moment(date).valueOf();
If the user is instructed actually enter a UTC date/time, then:
var expires = moment.utc(date).valueOf();

I use this method and it works. ValueOf does not work for me.
moment.utc(yourDate).format()

As of : moment.js version 2.24.0
let's say you have a local date input, this is the proper way to convert your dateTime or Time input to UTC :
var utcStart = new moment("09:00", "HH:mm").utc();
or in case you specify a date
var utcStart = new moment("2019-06-24T09:00", "YYYY-MM-DDTHH:mm").utc();
As you can see the result output will be returned in UTC :
//You can call the format() that will return your UTC date in a string
utcStart.format();
//Result : 2019-06-24T13:00:00
But if you do this as below, it will not convert to UTC :
var myTime = new moment.utc("09:00", "HH:mm");
You're only setting your input to utc time, it's as if your mentioning that myTime is in UTC, ....the output will be 9:00

This will be the answer:
moment.utc(moment(localdate)).format()
localdate = '2020-01-01 12:00:00'
moment(localdate)
//Moment<2020-01-01T12:00:00+08:00>
moment.utc(moment(localdate)).format()
//2020-01-01T04:00:00Z

moment.utc(date).format(...);
is the way to go, since
moment().utc(date).format(...);
does behave weird...

This worked for me. Others might find it useful.
let date = '2020-08-31T00:00:00Z'
moment.utc(moment(date).utc()).format() // returns 2020-08-30T22:00:00Z

If all else fails, just reinitialize with an inverse of your local offset.
var timestamp = new Date();
var inverseOffset = moment(timestamp).utcOffset() * -1;
timestamp = moment().utcOffset( inverseOffset );
timestamp.toISOString(); // This should give you the accurate UTC equivalent.

This moment.utc(stringDate, format).toDate() worked for me.
This moment.utc(date).toDate() not.

here, I'm passing the date object and converting it into UTC time.
$.fn.convertTimeToUTC = function (convertTime) {
if($(this).isObject(convertTime)) {
return moment.tz(convertTime.format("Y-MM-DD HH:mm:ss"), moment.tz.guess()).utc().format("Y-MM-DD HH:mm:ss");
}
};
// Returns if a value is an object
$.fn.isObject = function(value) {
return value && typeof value === 'object';
};
//you can call it as below
$(this).convertTimeToUTC(date);

Read this documentation of moment.js here.
See below example and output where I convert GMT time to local time (my zone is IST) and then I convert local time to GMT.
// convert GMT to local time
console.log('Server time:' + data[i].locationServerTime)
let serv_utc = moment.utc(data[i].locationServerTime, "YYYY-MM-DD HH:mm:ss").toDate();
console.log('serv_utc:' + serv_utc)
data[i].locationServerTime = moment(serv_utc,"YYYY-MM-DD HH:mm:ss").tz(self.zone_name).format("YYYY-MM-DD HH:mm:ss");
console.log('Converted to local time:' + data[i].locationServerTime)
// convert local time to GMT
console.log('local time:' + data[i].locationServerTime)
let serv_utc = moment(data[i].locationServerTime, "YYYY-MM-DD HH:mm:ss").toDate();
console.log('serv_utc:' + serv_utc)
data[i].locationServerTime = moment.utc(serv_utc,"YYYY-MM-DD HH:mm:ss").format("YYYY-MM-DD HH:mm:ss");
console.log('Converted to server time:' + data[i].locationServerTime)
Output is
Server time:2019-12-19 09:28:13
serv_utc:Thu Dec 19 2019 14:58:13 GMT+0530 (India Standard Time)
Converted to local time:2019-12-19 14:58:13
local time:2019-12-19 14:58:13
serv_utc:Thu Dec 19 2019 14:58:13 GMT+0530 (India Standard Time)
Converted to server time:2019-12-19 09:28:13

This worked for me:
const localtime = 1622516400000
moment(localtime).utc(true).format()

We can get 2 UTC date formats.
const date = '2021-07-20T18:30:00Z';
moment.utc(moment(date).utc()).format(); // 2021-07-19T18:30:00Z
moment.utc(moment(date).utc()).toISOString(); // 2021-07-20T18:30:00.000Z (Complete ISO-8601)

This works in my case.
Library: "moment": "^2.29.1",
moment().utc().format()

Don't you need something to compare and then retrieve the milliseconds?
For instance:
let enteredDate = $("#txt-date").val(); // get the date entered in the input
let expires = moment.utc(enteredDate); // convert it into UTC
With that you have the expiring date in UTC.
Now you can get the "right-now" date in UTC and compare:
var rightNowUTC = moment.utc(); // get this moment in UTC based on browser
let duration = moment.duration(rightNowUTC.diff(expires)); // get the diff
let remainingTimeInMls = duration.asMilliseconds();

how can change the text string to date object?

i am getting string from server and i need to covert that fetching string in to new date object.. for doing this, i tried this function, but no use, any one can help me to convert strings to date object?
my code is :
var nationZone = {
getNewYorkLocalTime : 'getTime.php?lat=40.71417&lan=74.00639',
getLondonLocalTime : 'getTime.php?lat=51.5&lan=0.1166667',
getChennaiLocalTime : 'getTime.php?lat=13.0833333&lan=80.2833333',
getBangaloreLocalTime:'getTime.php?lat=12.9833333&lan=77.5833333'
}
$.each(nationZone , function(key, value){
$.get(value, function(response){
var newdate = $(response).find('localtime').text();
if(key == "getNewYorkLocalTime"){
var newyourktime = new Date(newdate);
newyourktime.getTime()
}
});
});
but, the newyourktime is showing local time only.. any help please? as well i am getting the response from server is : 17 Nov 2011 18:09:47 - like this.

Use http://www.datejs.com/
As an example:
var newyourktime = Date.parse('2011-11-11, 11:11 AM');
alert(newyourktime.toString('dd/mm/yyyy HH:mm:ss EST'));
Check out the Datejs library documentation to meet your requirements, after your date string is parsed, you can do a lot with it.

This will try to parse the date using the client machine own local settings, which is not good.
Instead of passing it as string, pass it as the total seconds that passed since 1/1/1970 at midnight and use this number when constructing the new Date object of JavaScript.
For example pass this number: 1321614000000 and you will get November 18th 2011, 1 PM

You could use substr
day = newdate.substr(0,2);
month = newdate.substr(3,3);
year = newdate.substr(7,4);
var newyorktime = new Date(year, month, day);
Substr

Javascript: Extract a date from a string?

I have a string formatted as either
Today 3:28AM
Yesterday 3:28AM
08/22/2011 3:28AM
What I need to do is somehow extract into a variable the date portion of my string, ie. 'Today', 'Yesterday' or a date formatted as DD/MM/YYYY.
Is something like this possible at all with Javascript?

Since the JavaScript date parser won't recognize your dates, you can write a parser that puts the date into a format that it will recognize. Here is a function that takes the date examples that you gave and formats them to get a valid date string:
function strToDate(dateStr) {
var dayTimeSplit = dateStr.split(" ");
var day = dayTimeSplit[0];
var time = dayTimeSplit[1];
if (day == "Today") {
day = new Date();
} else if (day == "Yesterday") {
day = new Date();
day.setDate(day.getDate() - 1);
} else {
day = new Date(day);
}
var hourMinutes = time.substring(0, time.length -2);
var amPM = time.substring(time.length -2, time.length);
return new Date((day.getMonth() + 1) + "/" + day.getDate() + "/" + day.getFullYear()
+ " " + hourMinutes + " " + amPM);
}
Then you can call stroToDate to convert your date formats to a valid JavaScript Date:
console.log(strToDate("Today 3:28AM"));
console.log(strToDate("Yesterday 3:28AM"));
console.log(strToDate("08/22/2011 3:28AM"));
Outputs:
Sun Sep 25 2011 03:28:00 GMT-0700 (Pacific Daylight Time)
Sat Sep 24 2011 03:28:00 GMT-0700 (Pacific Daylight Time)
Mon Aug 22 2011 03:28:00 GMT-0700 (Pacific Daylight Time)

Obviously "Today" and "Yesterday" can never be transformed back to a real numeric date, for now it seems that what are you trying to do here is to save it as "Today" and "Yesterday", right?
It appears that the dd/mm/yyyy hh:mmxx you specified is always separated by a space.
so you can just split the string into two, and save the first part as your date.
the javascript function:
http://www.w3schools.com/jsref/jsref_split.asp
As for how to transform from "Today" back to 26/09/2011 etc, you need to seek solution from the XML side.

Here is a similar question: Javascript equivalent of php's strtotime()?
Here is the linked article: http://w3schools.com/jS/js_obj_date.asp
And the suggested solution:
Basically, you can use the date constructor to parse a date
var d=new Date("October 13, 1975 11:13:00");

There are a couple of ways you could do this. I will offer 2 of them.
option1:
If the day always at the beginning of the string you could capture the the first part by using a regular expression like /([a-z0-9]*)\s|([0-9]{1,})\/([0-9]{1,})\/([0-9]{1,})\s/ <- im not the best regex writer.
option2:
You could also do a positive look ahead if the time come immediately after the day (like your example above. Here is a link with the proper syntax for JS regex. http://www.javascriptkit.com/javatutors/redev2.shtml you can scroll down to lookaheads and see an example that should get you suared away there.

var reTYD = /(today|yesterday|\d{1,2}\/\d{1,2}\/\d{4})/i;
console.log( myString.match(reTYD) );