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javascript "date.getFullYear()" is returning 3991 [duplicate]

I have tried to get date and time from firebase timestamp as follows:
Date date=new Date(timestamp*1000);
SimpleDateFormat sfd = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
sfd.format(date);
but I'm getting results like:
:02-02-48450 04:21:54
:06-02-48450 10:09:45
:07-02-48450 00:48:35
as you can see the year is not as we live.
So, please help me to fix this.

Your timestamp 1466769937914 equals to 2016-06-24 12:05:37 UTC. The problem is that you are multiplying the timestamp by 1000. But your timestamp already holds a value in milliseconds not in seconds (this false assumption is most likely the reason you have the multiplication). In result you get 1466769937914000 which converted equals to 48450-02-01 21:51:54 UTC. So technically speaking all works fine and results you are getting are correct. All you need to fix is your input data and the solution is quite simple - just remove the multiplication:
SimpleDateFormat sfd = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
sfd.format(new Date(timestamp));

If you are looking to get a Date instance from Timestamp
If you need to get just the Date object from Timestamp, the Timestamp instance comes with a toDate() method that returns a Date instance.
For clarity:
Date javaDate = firebaseTimestampObject.toDate()

According to Firebase documentation, the types that are available JSON are:
String
Long
Double
Boolean
Map<String, Object>
List<Object>
Quoting another Stack Overflow post, I suggest you use JSON date string format yyyy-MM-dd'T'HH:mm:ss.SSSZ instead of epoch timestamp.
Comparing 1335205543511 to 2012-04-23T18:25:43.511Z, you can noticed that:
It's human readable but also succinct
It sorts correctly
It includes fractional seconds, which can help re-establish chronology
It conforms to ISO 8601
ISO 8601 has been well-established internationally for more than a decade and is endorsed by W3C, RFC3339, and XKCD

The .toDate() method should be all you need
You might like the docs here
As an added bonus, you might want very highly human readable output
Date only options
.toDate().toDateString()
.toDate().toLocaleDateString()
Time only options
.toDate().toTimeString()
.toDate().toLocaleTimeString()
Objects
However, if you are receiving an object you might do something like this
{JSON.stringify(createdAt.toDate()).replace(/['"]+/g, '')}
Converting the object into a string then replacing the quotes around the string.

firebase time is basically combination of seconds and nano seconds
time={
seconds:1612974698,
nanoseconds:786000000
}
total_miliseconds=(time.seconds+(time.nanoseconds)*0.00000001)*1000. // 1 nanosecond=1e-9 means 0.00000001
new Date(total_miliseconds)

String time=dataSnapshot.child("timeStamp").getValue().toString();
Long t=Long.parseLong(time);
Date myDate = new Date(t*1000);
Result
Fri May 11 05:37:58 GMT+06:30

For date, you can use this code :
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(time);
String date = DateFormat.format("dd-MM-yyyy", calendar).toString();
For time :
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(time);
String date = DateFormat.format("hh:mm", calendar).toString();

I think its bit late but easiest way is just:
(new Date(timestamp.toDate())).toDateString()

Within the Date() where you put your timestamp add
.toDate()
to the timestamp variable as #jasonleonhard said. Maybe just an example
new Date(timestamp.toDate())

Convert string to new Date object in UTC timeZONE

Can anyone let me know how to convert a string to a date Object with UTC time zone in ExtJs?
String is "2015-10-07T23:59:00". I would like to get the same in Date Object without changing the timezone.

First of all, your date string does not have a timezone.
When you make a JavaScript date object from a string, there are two possible outcomes you could expect:
You may want the date to be 23:59 Local (23:59 CEST in my case).
In this case, you want to use new Date("2015-10-07 23:59:00") with plain javascript (note the missing T), or Ext.Date.parse("2015-10-07T23:59:00","c");.
You may want the date to be 23:59 UTC (e.g. 01:59 CEST).
In this case, you want to use new Date("2015-10-07T23:59:00").
Of course, whenever you output the date, you have to get the date in the correct time zone as well. The console/toString will usually show it in local time. JavaScript does provide getUTC... methods if you require other time zones.
You see, using Time Zones with JavaScript is a painful experience. I would recommend to try moment.js if you need full time zone support.

You can use Ext.Date.parse.It gives Date Object as output.It syntax is:
Ext.Date.parse( String input, String format, [Boolean strict] )
For Example:
Ext.Date.parse("2015-10-07T23:59:00", "Y-m-dTH:i:s");

try
var millisFromEpoch = Date.parse('2015-10-07T23:59:00');
it will parse date in GMT timezone, Ext.date.parse use the current timezone instead

Given a date/time and timezone, how do you convert that into a UTC timestamp?

I am calling an API that returns a date/time string such as "2014-04-30 15:32:01". On top of this, I have a known timezone that this date/time exists in. I can see from the javascript Date() class has a .UTC() call for this, but that does not seem to accept a timezone as far as I can tell.
Given the date/time string + timezone, how can I convert those into a UTC timestamp?

I'd recommend using Moment.js and Moment Timezone.

You can create a timestamp using Date.parse from your local time (RFC2822 date format to include the timezone), create a date from that and use Date.toUTCString to get the UTC time. Not sure if it'll work with day light savings though.
Example: http://jsfiddle.net/3vXV6/ (will alert the date)
References:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toUTCString

Format date in a specific timezone

I'm using Moment.js to parse and format dates in my web app. As part of a JSON object, my backend server sends dates as a number of milliseconds from the UTC epoch (Unix offset).
Parsing dates in a specific timezone is easy -- just append the RFC 822 timezone identifier to the end of the string before parsing:
// response varies according to your timezone
const m1 = moment('3/11/2012 13:00').utc().format("MM/DD HH:mm")
// problem solved, always "03/11 17:00"
const m2 = moment('3/11/2012 13:00 -0400').utc().format("MM/DD HH:mm")
console.log({ m1, m2 })
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>
But how do I format a date in a specifc timezone?
I want consistent results regardless of the browser's current time, but I don't want to display dates in UTC.

As pointed out in Manto's answer, .utcOffset() is the preferred method as of Moment 2.9.0. This function uses the real offset from UTC, not the reverse offset (e.g., -240 for New York during DST). Offset strings like "+0400" work the same as before:
// always "2013-05-23 00:55"
moment(1369266934311).utcOffset(60).format('YYYY-MM-DD HH:mm')
moment(1369266934311).utcOffset('+0100').format('YYYY-MM-DD HH:mm')
The older .zone() as a setter was deprecated in Moment.js 2.9.0. It accepted a string containing a timezone identifier (e.g., "-0400" or "-04:00" for -4 hours) or a number representing minutes behind UTC (e.g., 240 for New York during DST).
// always "2013-05-23 00:55"
moment(1369266934311).zone(-60).format('YYYY-MM-DD HH:mm')
moment(1369266934311).zone('+0100').format('YYYY-MM-DD HH:mm')
To work with named timezones instead of numeric offsets, include Moment Timezone and use .tz() instead:
// determines the correct offset for America/Phoenix at the given moment
// always "2013-05-22 16:55"
moment(1369266934311).tz('America/Phoenix').format('YYYY-MM-DD HH:mm')

A couple of answers already mention that moment-timezone is the way to go with named timezone. I just want to clarify something about this library that was pretty confusing to me. There is a difference between these two statements:
moment.tz(date, format, timezone)
moment(date, format).tz(timezone)
Assuming that a timezone is not specified in the date passed in:
The first code takes in the date and assumes the timezone is the one passed in.
The second one will take date, assume the timezone from the browser and then change the time and timezone according to the timezone passed in.
Example:
moment.tz('2018-07-17 19:00:00', 'YYYY-MM-DD HH:mm:ss', 'UTC').format() // "2018-07-17T19:00:00Z"
moment('2018-07-17 19:00:00', 'YYYY-MM-DD HH:mm:ss').tz('UTC').format() // "2018-07-18T00:00:00Z"
My timezone is +5 from utc. So in the first case it does not change and it sets the date and time to have utc timezone.
In the second case, it assumes the date passed in is in -5, then turns it into UTC, and that's why it spits out the date "2018-07-18T00:00:00Z"
NOTE: The format parameter is really important. If omitted moment might fall back to the Date class which can unpredictable behaviors
Assuming the timezone is specified in the date passed in:
In this case they both behave equally
Even though now I understand why it works that way, I thought this was a pretty confusing feature and worth explaining.

Use moment-timezone
moment(date).tz('Europe/Berlin').format(format)
Before being able to access a particular timezone, you will need to load it like so (or using alternative methods described here)
moment.tz.add('Europe/Berlin|CET CEST CEMT|-10 -20 -30')

.zone() has been deprecated, and you should use utcOffset instead:
// for a timezone that is +7 UTC hours
moment(1369266934311).utcOffset(420).format('YYYY-MM-DD HH:mm')

I was having the same issue with Moment.js. I've installed moment-timezone, but the issue wasn't resolved. Then, I did just what here it's exposed, set the timezone and it works like a charm:
moment(new Date({your_date})).zone("+08:00")
Thanks a lot!

Just came acreoss this, and since I had the same issue, I'd just post the results I came up with
when parsing, you could update the offset (ie I am parsing a data (1.1.2014) and I only want the date, 1st Jan 2014. On GMT+1 I'd get 31.12.2013. So I offset the value first.
moment(moment.utc('1.1.2014').format());
Well, came in handy for me to support across timezones
B

If you pass the timestamp as the parameter to moment() (e.g if the timezone is Asia/Hong_kong which is +08:00), what I do is:
const localDateTime = moment((item.createdAt.seconds + 8 * 3600) * 1000).format('YYYY-MM-DD HH:mm:ss');

You can Try this ,
Here you can get the date based on the Client Timezone (Browser).
moment(new Date().getTime()).zone(new Date().toString().match(/([-\+][0-9]+)\s/)[1]).format('YYYY-MM-DD HH:mm:ss')
The regex basically gets you the offset value.
Cheers!!

JS Dates only with UTC timezone

Is there some way to tell Javascript that it should never use anything but the UTC timezone?
When I create a new Date object, it gets my browsers timezone, but this will muck up when transporting via JSON.
All dates and times in the app are naive and has no use for the users timezone. So creating and working with only UTC times would be just fine, but no matter what I do, I just get what my date would look like in UTC and thats just not good enough.
I am using Bakcbone and DateJS if that makes any difference.
Any ideas on this?

Instead of transporting the string representation of the date, new Date().milliseconds. This is the UNIX time, i.e.
Integer value representing the number of milliseconds since 1 January
1970 00:00:00 UTC.
and therefore independent of the timezone.
Alternatively, construct the date string yourself, but use the getUTC* methods:
var d = new Date();
alert("It's " + d.getUTCHours() + ':' + d.getUTCSeconds());

I ended up just using .toString() and sending that along with the JSON post. Seemed like the simplest thing to do.