James Padolsey» Uncategorized category – James Padolsey http://james.padolsey.com Just another WordPress weblog Sat, 21 Aug 2010 04:38:19 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 Getting the real time in JavaScript http://james.padolsey.com/uncategorized/getting-the-real-time-in-javascript/ http://james.padolsey.com/uncategorized/getting-the-real-time-in-javascript/#comments Thu, 29 Jan 2009 00:03:51 +0000 James http://james.padolsey.com/?p=477 Date constructor will give us the time as set on the user's computer, but what if we want the accurate time, or the time in a different timezone?]]> Getting the time in JavaScript is pretty simple. Using the Date constructor will give us the time as set on the user’s computer, but what if we want the accurate time, or the time in a different timezone?

Even with getTimezoneOffset() you’re still relying on the client!

It turns out that the only way of getting a complete and accurate time from any timezone requires a little bit of server interaction. Luckily there are a few APIs out there that offer this service (actually, there’s only one; well I couldn’t find any others)!

Here we’re using the ‘json-time’ API developed by Simon Willson:

JSON-time

function getTime(zone, success) {
    var url = 'http://json-time.appspot.com/time.json?tz=' + zone,
        ud = 'json' + (+new Date());
    window[ud]= function(o){
        success && success(new Date(o.datetime), o);
    };
    document.getElementsByTagName('head')[0].appendChild((function(){
        var s = document.createElement('script');
        s.type = 'text/javascript';
        s.src = url + '&callback=' + ud;
        return s;
    })());
}

Usage

The first parameter of the callback function is the time (having been passed through the Date constructor), so you can use Date methods such as getSeconds() etc. The second parameter is the entire object returned from the JSON request.

// Alert GMT:
getTime('GMT', function(time){
    alert(time);
});
 
// Get London time, and format it:
getTime('Europe/London', function(time){
    var formatted = time.getHours() + ':' 
                  + time.getMinutes() + ':'
                  + time.getSeconds();
    alert( 'The time in London is ' + formatted );
});

For reference, here’s a list of all the available timezones (to use one, remove the backslash).

jQuery version

$.getTime = function(zone, success) {
    var url = 'http://json-time.appspot.com/time.json?tz='
            + zone + '&callback=?';
    $.getJSON(url, function(o){
        success && success(new Date(o.datetime), o);
    });
};
 
// Usage:
$.getTime('GMT', function(time){
    alert(time);
});

MooTools version

You’ll need to download the JsonP class.

function getTime(zone, success) {
    var url = 'http://json-time.appspot.com/time.json';
    new JsonP(url, {
        data: { tz: zone },
        onComplete: function(o){
            success && success(new Date(o.datetime), o);
        }
    }).request();
}
 
// Usage:
getTime('GMT', function(time){
    alert(time);
});

Thank you Simon Willison for making this API; seriously, I searched around the entire internets just for one damn API and I almost lost hope!

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