timeago.js

var DateHelper = {
  // Takes the format of "Jan 15, 2007 15:45:00 GMT" and converts it to a relative time
  // Ruby strftime: %b %d, %Y %H:%M:%S GMT
  time_ago_in_words_with_parsing: function(from) {
    var date = new Date;
    date.setTime(Date.parse(from));
    return this.time_ago_in_words(date);
  },
  // Takes a timestamp and converts it to a relative time
  // DateHelper.time_ago_in_words(1331079503000)
  time_ago_in_words: function(from) {
    return this.distance_of_time_in_words(new Date, from);
  },

  distance_of_time_in_words: function(to, from) {
    var distance_in_seconds = ((to - from) / 1000);
    var distance_in_minutes = Math.floor(distance_in_seconds / 60);
    var tense = distance_in_seconds < 0 ? " from now" : " ago";
    distance_in_minutes = Math.abs(distance_in_minutes);
    if (distance_in_minutes == 0) { return 'less than a minute'+tense; }
    if (distance_in_minutes == 1) { return 'a minute'+tense; }
    if (distance_in_minutes < 45) { return distance_in_minutes + ' minutes'+tense; }
    if (distance_in_minutes < 90) { return 'about an hour'+tense; }
    if (distance_in_minutes < 1440) { return 'about ' + Math.floor(distance_in_minutes / 60) + ' hours'+tense; }
    if (distance_in_minutes < 2880) { return 'a day'+tense; }
    if (distance_in_minutes < 43200) { return Math.floor(distance_in_minutes / 1440) + ' days'+tense; }
    if (distance_in_minutes < 86400) { return 'about a month'+tense; }
    if (distance_in_minutes < 525960) { return Math.floor(distance_in_minutes / 43200) + ' months'+tense; }
    if (distance_in_minutes < 1051199) { return 'about a year'+tense; }

    return 'over ' + Math.floor(distance_in_minutes / 525960) + ' years';
  }
};

module.exports = DateHelper;