Create a Date With a Set Timezone Without Using a String Representation

Create a Date with a set timezone without using a string representation

using .setUTCHours() it would be possible to actually set dates in UTC-time, which would allow you to use UTC-times throughout the system.

You cannot set it using UTC in the constructor though, unless you specify a date-string.

Using new Date(Date.UTC(year, month, day, hour, minute, second)) you can create a Date-object from a specific UTC time.

Parse date without timezone javascript

The date is parsed correctly, it's just toString that converts it to your local timezone:

let s = "2005-07-08T11:22:33+0000";
let d = new Date(Date.parse(s));

// this logs for me 
// "Fri Jul 08 2005 13:22:33 GMT+0200 (Central European Summer Time)" 
// and something else for you

console.log(d.toString()) 

// this logs
// Fri, 08 Jul 2005 11:22:33 GMT
// for everyone

console.log(d.toUTCString())

Setting UTC timezone with numeric values in JS [UTC+2, UTC+3, UTC-12, etc]

I tried to use moment.js but...

Didn't you come accross those methods: .utc(), .add() and .format() ?

EDIT

To accomodate non-full hour offsets, you can use .match to retreive the sign (+ or -) of the offset, the hour and the optionnal minute.

Here is the actual possible offsets list: Wikipedia

It outputs UTC time if your offset only is UTC or is an empty string.

const timeOffsets = ["UTC+2", "UTC+3", "UTC-12", "UTC+5:45", "UTC-3:30", "UTC", ""]

function getlocalTime(offset) {
  const time = offset.match(/([\+\-])(\d{1,2}):?(\d{2})?/)
  let sign = ""
  let numericOffset = 0
  if (time) {
    sign = time[1]
    numericOffset = parseInt(time[2]) + (time[3] ? parseInt(time[3]) / 60 : 0)
  }

  return moment().utc().add(sign + numericOffset, "hours").format("YYYY-MM-DD HH:mm:ss")
}

const result = timeOffsets.map(getlocalTime)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.4/moment.min.js"></script>

Convert Date/Time for given Timezone - java

For me, the simplest way to do that is:

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

//Here you say to java the initial timezone. This is the secret
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
//Will print in UTC
System.out.println(sdf.format(calendar.getTime()));    

//Here you set to your timezone
sdf.setTimeZone(TimeZone.getDefault());
//Will print on your default Timezone
System.out.println(sdf.format(calendar.getTime()));

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