Super simple library for date time formatting.

dateutil.js

var dateUtil = function () {
  var monthDict = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
  return {
    time: function (date) {
      var hour = date.getHours(),
          min = date.getMinutes() + "",
          ampm = 'AM';

      if (hour == 0) {
        hour = 12;
      } else if (hour == 12) {
        ampm = 'PM';
      } else if (hour > 12) {
        hour -= 12;
        ampm = 'PM';
      }

      if (min.length == 1) {
        min = '0' + min;
      }

      return hour + ':' + min + ' ' + ampm;
    },
    date: function (date) {
      var mon = monthDict[date.getMonth()],
          day = date.getDate()+'',
          dayi = ~~(day),
          year = date.getFullYear(),
          thisyear = (new Date()).getFullYear(),
          th = 'th';

      // anti-'th' - but don't do the 11th, 12th or 13th
      if ((dayi % 10) == 1 && day.substr(0, 1) != '1') {
        th = 'st';
      } else if ((dayi % 10) == 2 && day.substr(0, 1) != '1') {
        th = 'nd';
      } else if ((dayi % 10) == 3 && day.substr(0, 1) != '1') {
        th = 'rd';
      }

      if (day.substr(0, 1) == '0') {
        day = day.substr(1);
      }

      return mon + ' ' + day + th + (thisyear != year ? ', ' + year : '');
    },
    shortdate: function (date) {
      var mon = monthDict[date.getMonth()],
          day = date.getDate()+'',
          year = date.getFullYear(),
          thisyear = (new Date()).getFullYear();

      if (thisyear === year) {
        return day + ' ' + mon;
      } else {
        return day + ' ' + mon + (year+'').substr(2, 2);
      }
    },
    datetime: function (date) {
      return this.time(date) + ' ' + this.date(date);
    },
    relative: function (date) {
      var relative_to = (arguments.length > 1) ? arguments[1] : new Date(),
          delta = ~~((relative_to.getTime() - date.getTime()) / 1000),
          r = '';

      delta = delta + (relative_to.getTimezoneOffset() * 60);

      if (delta <= 1) {
        r = '1 second ago';
      } else if (delta < 60) {
        r = delta + ' seconds ago';
      } else if (delta < 120) {
        r = '1 minute ago';
      } else if (delta < (45*60)) {
        r = (~~(delta / 60)) + ' minutes ago';
      } else if (delta < (2*90*60)) { // 2* because sometimes read 1 hours ago
        r = '1 hour ago';
      } else if (delta < (24*60*60)) {
        r = (~~(delta / 3600)) + ' hours ago';
      } else {
        r = this.shortdate(date);
      }

      return r;
    }    
  };
}();