prettydates.js

/*
 * JavaScript Pretty Date
 * Copyright (c) 2011 John Resig (ejohn.org)
 * Licensed under the MIT and GPL licenses.

 * prettyDate("2008-01-28T20:24:17Z") // => "2 hours ago"
 * prettyDate("2008-01-27T22:24:17Z") // => "Yesterday"
 * prettyDate("2008-01-26T22:24:17Z") // => "2 days ago"
 * prettyDate("2008-01-14T22:24:17Z") // => "2 weeks ago"
 * prettyDate("2007-12-15T22:24:17Z") // => undefined
 * Takes an ISO time and returns a string representing how
 * long ago the date represents.
 */
function prettyDate(time) {
    var date = new Date((time || "").replace(/-/g, "/").replace(/[TZ]/g, " ")),
        diff = (((new Date()).getTime() - date.getTime()) / 1000),
        day_diff = Math.floor(diff / 86400);

    if (isNaN(day_diff) || day_diff < 0 || day_diff >= 31) return;

    return day_diff == 0 && (
    diff < 60 && "just now" ||
      diff < 120 && "1 minute ago" ||
      diff < 3600 && Math.floor(diff / 60) + " minutes ago" ||
      diff < 7200 && "1 hour ago" ||
      diff < 86400 && Math.floor(diff / 3600) + " hours ago") ||
      day_diff == 1 && "Yesterday" ||
      day_diff < 7 && day_diff + " days ago" ||
      day_diff < 31 && Math.ceil(day_diff / 7) + " weeks ago";
}

// If jQuery is included in the page, adds a jQuery plugin to handle it as well
if (typeof jQuery != "undefined") jQuery.fn.prettyDate = function() {
    return this.each(function() {
        var date = prettyDate(this.title);
        if (date) jQuery(this).text(date);
    });
};