See example: http://jsfiddle.net/jmervine/dqA9r/5/

FormattedDate.js

/* 
Author: Joshua P. Mervine <[email protected]> [github.com/jmervine]

See: http://jsfiddle.net/jmervine/dqA9r/5/

Use:

<script src="http://cdn.mervine.net/FormattedDate.js" />
<script src="http://cdn.mervine.net/FormattedDate.min.js" />

var d = new FormattedDate("Tue Mar 25 2014 13:53:34 GMT-0700 (PDT)");
d.stringify();
=> 1 hour ago

var d = new FormattedDate("Tue Mar 25 2014 09:23:34 GMT-0700 (PDT)");
d.stringify();
=> 5 hours ago

var d = new FormattedDate("Mon Mar 24 2014 02:23:34 GMT-0700 (PDT)");
d.stringify();
=> 03/25/2014 02:23:34

var d = new FormattedDate();
d.stringify();
=> 0 minutes ago
d.stringify('day');
=> 26
d.stringify('month');
=> 03
d.stringify('year');
=> 2014
d.stringify('hour');
=> 14
d.stringify('minute');
=> 23
d.stringify('seconds');
=> 34
d.stringify('ms');
=> 845
d.stringify('day_name');
=> Monday
d.stringify('something bad');
=> undefined
d.format('MN - DN - HH:mm:ss MSms');
=> March - Monday - 14:23:34 845ms
    
 */

function FormattedDate() {
    var args = Array.prototype.concat.apply([null], arguments);
    var days = [ "Sunday", "Monday", "Tuesday", "Wednesday", 
                     "Thursday", "Friday", "Saturday" ];
    
    var months = ["January", "Feburary", "March", "April", "May", "June", "July", 
                     "August", "September", "October", "November", "December"];
    
    this.date = this.now = new (Function.prototype.bind.apply(Date, args));
    
    this.day = this.days = this.date.getDate()+1;
    this.dayName = this.dayname = this.day_name = days[this.date.getDay()-1];
    this.dayShort = this.dayshort = this.day_short = this.dayName.slice(0,3);
    
    this.month = this.months = this.mo = this.mos = this.date.getMonth()+1;
    this.monthName = this.monthname = this.month_name = months[this.month-1];
    this.monthShort = this.monthshort = this.month_short = this.monthName.slice(0,3);
    
    this.year = this.years = this.yr = this.yrs = this.date.getFullYear();
    
    this.hour = this.hours = this.hr = this.hrs = this.date.getHours();
    this.minute = this.minutes = this.min = this.date.getMinutes();
    this.second = this.seconds = this.sec = this.secs = this.date.getSeconds();
    
    this.millisecond = this.milliseconds = this.ms = this.date.getMilliseconds();
    
    this.time = this.epoch = this.date.getTime();

    this.today  = !!(new Date(new Date()-(24*60*60*1000)) < this.date);
}

FormattedDate.prototype = {
    stringify: function stringify(entity, format) {
        format = format || "MM/DD/YY HH:mm:ss";
        
        if (entity) {
            if (typeof this[entity] === 'string') return this[entity];
            
            if (entity !== 'date') {
                var num = this[entity];
                if (num < 10) return "0"+num;
                return ""+num;
            }
        }
        
        if (this.today) {
            var now = new FormattedDate();
            var hoursAgo = (now.hour - this.hour);
            
            var s = "s";
            
            if (hoursAgo === 0) {
                var minutesAgo = (now.minute - this.minute);
                if (minutesAgo === 1) s = "";
                return minutesAgo + " minute" + s +" ago";
            }
            
            if (hoursAgo === 1) s = "";
            return hoursAgo + " hour" + s + " ago";
        }
        
        return this.format(format);
    },
    format: function(str) {
        var mapping = { 'YY': 'yr', 'MM': 'mo', 'DD': 'day', 'dd': 'day', 
            'HH': 'hr', 'hh': 'hr', 'mm': 'min', 'SS': 'sec', 'ss': 'sec',
            'DN': 'dayName', 'MN': 'monthName', 'MS': 'ms' };
        
        var that = this;
        Object.keys(mapping).forEach(function(map) {
            str = str.replace(map, that.stringify(mapping[map]), "g");
        });
        return str;
    }
};

FormattedDate.min.js

/* author: github.com/jmervine, compressed via http://jscompress.com/ */ 
function FormattedDate(){var e=Array.prototype.concat.apply([null],arguments);var t=["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"];var n=["January","Feburary","March","April","May","June","July","August","September","October","November","December"];this.date=this.now=new(Function.prototype.bind.apply(Date,e));this.day=this.days=this.date.getDate()+1;this.dayName=this.dayname=this.day_name=t[this.date.getDay()-1];this.dayShort=this.dayshort=this.day_short=this.dayName.slice(0,3);this.month=this.months=this.mo=this.mos=this.date.getMonth()+1;this.monthName=this.monthname=this.month_name=n[this.month-1];this.monthShort=this.monthshort=this.month_short=this.monthName.slice(0,3);this.year=this.years=this.yr=this.yrs=this.date.getFullYear();this.hour=this.hours=this.hr=this.hrs=this.date.getHours();this.minute=this.minutes=this.min=this.date.getMinutes();this.second=this.seconds=this.sec=this.secs=this.date.getSeconds();this.millisecond=this.milliseconds=this.ms=this.date.getMilliseconds();this.time=this.epoch=this.date.getTime();this.today=!!(new Date(new Date-24*60*60*1e3)<this.date)}FormattedDate.prototype={stringify:function(t,n){n=n||"MM/DD/YY HH:mm:ss";if(t){if(typeof this[t]==="string")return this[t];if(t!=="date"){var r=this[t];if(r<10)return"0"+r;return""+r}}if(this.today){var i=new FormattedDate;var s=i.hour-this.hour;var o="s";if(s===0){var u=i.minute-this.minute;if(u===1)o="";return u+" minute"+o+" ago"}if(s===1)o="";return s+" hour"+o+" ago"}return this.format(n)},format:function(e){var t={YY:"yr",MM:"mo",DD:"day",dd:"day",HH:"hr",hh:"hr",mm:"min",SS:"sec",ss:"sec",DN:"dayName",MN:"monthName",MS:"ms"};var n=this;Object.keys(t).forEach(function(r){e=e.replace(r,n.stringify(t[r]),"g")});return e}}