Javascript DateFormat For Different Timezones

I'm a Java developer and I'm used to the SimpleDateFormat class that allows me to format any date to any format by settings a timezone. Date date = new Date(); SimpleDateFormat sd

Solution 1:

There is a way to format for time zones.

console.log(new Date().toLocaleDateString('en-US', {timeZone: 'America/Denver'}))
// 11/13/2018
console.log(new Date().toLocaleTimeString('en-US', {timeZone: 'America/Denver'}))
// 2:30:54 PM
console.log(new Date().toLocaleTimeString('en-US', {timeZone: 'America/New_York'}))
// 4:31:26 PM

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleDateString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleTimeString

Solution 2:

The ISO Extended format for common date is YYYY-MM-DD, and for time is hh:mm:ss. Either format can be understood, unambiguously, worldwide.

See also: http://jibbering.com/faq/#dates

Solution 3:

If you're just passing the raw TZ there's nothing really complicated about adjusting the hours. My example below is of course abbreviated. Yours may get quite long depending on how many patterns you'd handle.

Date.prototype.format = function(format, tzAdjust) {
    // adjust timezone
    this.setHours(this.getHours()+tzAdjust)
    // pad zero helper - return "09" or "12"
    var two = function(s){ return s+"".length==1 ? "0"+s : s+""; }
    // replace patterns with date numbers
    return format.replace(/dd|MM|yyyy|hh|mm|ss/g, function(pattern){
        switch(pattern){
            case "d" : return this.getDate();
            case "dd" : return two(this.getDate());
        }
    });
}

Solution 4:

Don't write your own stuff; just get datejs: http://www.datejs.com/

You can figure out what the timezone offset is set to in the execution environment like this:

var local = new Date();
var utc = Date.UTC(local.getFullYear(), local.getMonth(), local.getDate(), local.getHours(), local.getMinutes(), local.getSeconds(), local.getMilliseconds());
var tz = (utc - local.getTime()) / (60 * 60 * 1000);

Solution 5:

Attempting to (ever so slightly) improve upon mwilcox's suggestion:

Date.prototype.format = function(format, tzAdjust) {

    // get/setup a per-date-instance tzDate object store
    var tzCache = this.__tzCache = this.__tzCache || (this.__tzCache = {});

    // fetch pre-defined date from cache 
    var tzDate = tzCache[tzAdjust];
    if ( !tzDate )
    {
      // on miss - then create a new tzDate and cache it
      tzDate = tzCache[tzAdjust] = new Date( this );
      // adjust by tzAdjust (assuming it's in minutes 
      // to handle those weird half-hour TZs :) 
      tzDate.setUTCMinutes( tzDate.getUTCMinutes()+tzAdjust );
    }

    return format.replace(/dd|MM|yyyy|hh|mm|ss/g, function(pattern){
               // replace each format tokens with a value 
               // based on tzDate's corresponding UTC property
             });
}