Develop Reference

MomentJs Format One Day Behind

I have seen a question that is similar to mine (Moment.js sets dates to 1 day behind) but I can't seem to apply it.
Essentially, my date gets parsed like this:
var date = moment("2019-05-27T00:00:00Z"); // date is the 27th
When I format it to get the day, expecting the 27th, I instead receive the 26th!
date.format("DD")
Does anyone know why this might be happening and how to correct it?
http://jsfiddle.net/rmdxj26e/

You must use moment.utc(), the Moment documentation says:
By default, moment parses and displays in local time.
If you want to parse or display a moment in UTC, you can use
moment.utc() instead of moment().
This brings us to an interesting feature of Moment.js. UTC mode.
While in UTC mode, all display methods will display in UTC time
instead of local time.
moment().format(); // 2013-02-04T10:35:24-08:00
moment.utc().format(); // 2013-02-04T18:35:24+00:00
jsFiddle Output:
Live example:
var date = moment.utc("2019-05-27T00:00:00Z");
$('#date').append($('<p>').html(date.format("DD")));
$('#date').append($('<p>').html(date.local().format("DD")));
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="date"></div>

The problem is the format of the parsed date. The Z letter means it is a "Zulu time" (UTC). I don't know what is your timezone, but the date is converted to your timezone.
You can parse local time format (without Z) and it should display properly.
So the full code with explanation:
var date = moment("2019-05-27T00:00:00"); // date is the 27th in local time
$('#date').append($('<p>').html(date.utc().format("DD"))); // can display 26th or 27th depends on local timezone on the PC
$('#date').append($('<p>').html(date.local().format("DD"))); // is still local so it will be 27th

Convert hour to date time without adding +1

Hi im using moment js to convert this string 20:00 I tried:
var a = moment("20:00", "HH:mm")
console.log(a.format()) // 2016-09-08T20:00:00+01:00
the problem when I store in mongodb it become
2016-09-10T19:00:00.000Z
I want to store 2016-09-10T20:00:00.000Z
anyway can explain why please ?

When you say that you want to store 2016-09-10T20:00:00.000Z what you are saying is that you want to assume that your date and time is UTC.
To assume that the date you are parsing is a UTC value, use moment.utc
var a = moment.utc("20:00", "HH:mm")
console.log(a.format()) // 2016-09-08T20:00:00Z
Note that when you parse a time without a date, moment assumes the current date. This may not be the behavior that you want.
I'm also not sure if you want a UTC date (which is what you are saying), or a local date without an offset indicator. If you want a local date without an offset indicator, simply use a format without an offset:
moment.utc("20:00", "HH:mm").format('YYYY-MM-DDTHH:mm:ss.SSS')
"2016-09-08T20:00:00.000"
If you are dealing with local dates that do not have a time zone association, I recommend using moment.utc to parse, as this will ensure that the time does not get shifted to account for DST in the current time zone.
For more information about how to parse dates into the time zone or offset that you would like in moment, see my blog post on the subject.

This it how it should look:
var a = moment("20:00", "HH:mm")
console.log(a.utcOffset('+0000').format())
<script src="http://momentjs.com/downloads/moment.min.js"></script>
Doe, the problem is that you are using timezones when you create the date.
MomentJS uses your current timezone automatically.
Mongo however saves the time as it would be in another timezone.
Therefore, if you want the two strings to format the same way, you need to set the timezone.

Getting Time Zone Name(IST,PST,DST) of system's date in java-script in IE

I am trying to fetch the time zone name of my system's date in java-script.
In Chrome and firefox i am able to do that but in case of IE it gives me the following output
var date = new date()
my date comes out to be ("Wed Nov 27 17:46:24 UTC+0530 2013").
Clearly it does not give me any information about the time zone name.
One way is to use "UTC+0530" and then fetch the name, but two Time Zones exist
corresponding to this value. So not be possible.
Please suggest.

There is this javascript library which you might want to give a try:
jsTimezoneDetect : http://pellepim.bitbucket.org/jstz/
Example:
var timezone = jstz.determine();
timezone.name();
--> "Asia/Kolkata"

Java Script: How to ammend a datetime variable to set a specific time?

I need to take a datetime values from an MSSQL based app which is read into the script as 22/12/2010 3:56pm and adjsut the time component toa set time.
I've used what I know of javascript and what I can find in google searches to try and progress this but to no avail.
Premis: I need to read the date time value and set the time portion of the date to 8am, 1pm or 4pm dependent on another field.
The conditional logic portion of the script is fine the date functions aren't so fine.
Current code I'm currently using:
if(fldPriority.Value=='2')
{
var ResDate = new Date(fldTargetResolutionTime.Value);
var newdate = new Date(ResDate.getYear(),ResDate.GetMonth(),ResDate.GetDay(),16,0,0,0);
objReturn = newdate
}
Problem:
The date reads in originally in gmt format 22/12/2010 3:56pm but then gets changes to utc format and the date changes significantly to Wed Oct 12 15:56:00 UTC+12 2011
Any help would be greatly appreciated.

Make a copy of the Date and set the time using UTCHours.
The return value will be the correct Date and time,
but you if need to convert it to a string the string will be local time unless you call newDate.toUTCString();
(or objReturn.toUTCString())
var newdate=new Date(ResDate);
newDate.setUTCHours(16,0,0,0);
objReturn=newDate;

How to get difference of saved time and current time in jquery?

I want to get the time difference between saved time and current time in javascript or jquery. My saved time looks like Sun Oct 24 15:55:56 GMT+05:30 2010.
The date format code in java looks like
String newDate = "2010/10/24 15:55:56";
DateFormat format = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = format.parse(newDate);
How to compare it with the current time and get the difference?
Is there any inbuilt function in jquery or javascript??
Any suggestions or links would be appreciative!!!
Thanks in Advance!
Update
Date is stored as varchar in the DB. I am retriving it to a String variable and then change it to java.util.Date object. The java code looks like
String newDate = "2010/10/24 15:55:56";
DateFormat format = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = format.parse(newDate);
This date object was sent to client. There i want to compare the saved date with current date and want to show the time difference like 2 secs ago, 2 hours ago, 2 days ago etc... like exactly in facebook. I have gone through some date to timestamp conversion tutorial in java script and now i can get the difference in timestamp. Now, i want to know how i shall change it to some format like "2 secs or 2 days or 24 hours"??. Or, how i shall change it back to date format???

Convert them into timestamps which are actually integers and can get subtracted from each other. The you just have to convert back the resulting timestamp to a javascript date object.
var diff = new Date();
diff.setTime( time2.getTime()-time1.getTime() );

You dont need to explicit convert, just do this:
var timediff = new Date() - savedTime;
This will return the difference in milliseconds.

jQuery doesn't add anything for working with dates. I'd recommend using Datejs in the event that the standard JavaScript Date API isn't sufficient.
Perhaps you could clarify exactly what input and output you're aiming for. What do you mean by "the difference?" There is more than one way to express the difference between to instants in time (primarily units and output string formatting).
Edit: since you said you're working with jQuery, how about using CuteTime? (Demo page)