datetime module for ISO8601 UTC Dates

datetime.js

define([

], function(){

    var months = ['January', 'February', 'March', 'April', 'May',
                  'June', 'July', 'August', 'September', 'October',
                  'November', 'December'];

    // All values assumed to be ISO 8601 and in UTC
    // 2013-08-29T14:29Z
    // 2013-08-29T14:29.000Z
    // 2013-08-29T14:29+0000
    // 2013-08-29T14:29:30.123+0000
    var isoRegex = /(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(?:\:(\d{2})(?:\.(\d+))?)?(?:Z|\+0000)?/;

    function UTCStringToMilliseconds(value){
        // 2013-08-29T15:02:00Z
        // milliseconds and seconds are optional
        // if omitted, 0's are assumed.
        var c = isoRegex.exec(value);
        var year, month, day, hours, minutes, seconds, millisecond = 0;
        year = c[1];
        month = (c[2] - 1);
        day = c[3];
        hour = c[4];
        minute = c[5];
        second = c[6] || 0;
        millisecond = c[7] || 0;

        return Date.UTC(year, month, day, hour, minute, second, millisecond);
    }

    function UTCStringToSeconds(value){
        var utcMilliSeconds = UTCStringToMilliseconds(value);
        return parseInt((utcMilliSeconds / 1000), 10);
    }

    function UTCStringToLocalDate(value){
        var utcSeconds = UTCStringToSeconds(value);
        var date = new Date(0);

        date.setUTCSeconds(utcSeconds);
        return date;
    }

    function monthDayYearStringForDate(date){
        var dayValue = date.getDate();
        var suffix = daySuffix(day);
        var day = dayValue.toString() + suffix;

        return months[date.getMonth()] + ' ' + day + ' ' + date.getFullYear();
    }

    function monthDayYearStringForUTCString(value){
        var date = UTCStringToLocalDate(value);
        return monthDayYearStringForDate(date);
    }

    function daySuffix(day){
        switch (day)
        {
            case 1:
            case 21:
            case 31:
                return 'st';
            case 2:
            case 22:
                return 'nd';
            case 3:
            case 23:
                return 'rd';
            default:
                return 'th';
        }
    }

    function relativeDate(value){
        // compatibility
        var now = +new Date();
        var date = UTCStringToMilliseconds(value);

        var totalSeconds = parseInt((now - date) / 1000, 10);
        var time = '';

        if (totalSeconds < 10) {
            return 'just now';

        } else if(totalSeconds < 60) {
            time = totalSeconds;
            return time + ' seconds ago';

        } else if(totalSeconds < 120) {
            return 'about a minute ago';

        } else if(totalSeconds < 3600) {
            time = parseInt(totalSeconds / 60, 10);
            return time + ' minutes ago';

        } else if(totalSeconds < 7200) {
            return 'about an hour ago';

        } else if(totalSeconds < 86400) {
            time = parseInt(totalSeconds / 3600, 10);
            return time + ' hours ago';

        } else if(totalSeconds < 172800) {
            return '1 day ago';

        } else if(totalSeconds < 604800) {
            time = parseInt(totalSeconds / 86400, 10);
            return time + ' days ago';

        } else if(totalSeconds < 1209600) {
            return '1 week ago';

        } else {
            time = parseInt(totalSeconds / 604800, 10);
            return time + ' weeks ago';
        }
    }

    return {
        relativeDate: relativeDate,
        UTCStringToMilliseconds: UTCStringToMilliseconds,
        UTCStringToSeconds: UTCStringToSeconds,
        UTCStringToLocalDate: UTCStringToLocalDate,
        monthDayYearStringForDate: monthDayYearStringForDate,
        monthDayYearStringForUTCString:monthDayYearStringForUTCString
    };
});

Parses ISO 8601 UTC Dates to JS Local Time Dates. Includes some relative date formatting as some simple date formatting. Should handle the following formats:

2013-08-29T14:29Z
2013-08-29T14:29:00Z
2013-08-29T14:29:00.000Z
2013-08-29T14:29+0000
2013-08-29T14:29:00+0000
2013-08-29T14:29:00.000+0000

If seconds or milliseconds are not present, 0 is assumed.