Number of years, months, and days between today and some date in the past. Avoids problems associated with leap years and inconsistent total days in a given month.

gistfile1.js

var yearsMonthsDaysBetween = function(date) {
    var andString, days, daysString, months, monthsString, s, today, years, yearsString;
    today = new Date();
    date = new Date(date);
    years = today.getFullYear() - date.getFullYear();
    months = today.getMonth() - date.getMonth();
    days = today.getDate() - date.getDate();
    if (days < 0) {
      months -= 1;
      days = Math.floor((today - new Date(today.getFullYear(), today.getMonth() - 1, date.getDate())) / 1000 / 60 / 60 / 24);
    }
    if (months < 0) {
      years -= 1;
      months += 12;
    }
    s = function(n) {
      return ["s", "", "s"][Math.min(n, 2)];
    };
    yearsString = years ? "" + years + " year" + (s(years)) + ", " : "";
    monthsString = months ? "" + months + " month" + (s(months)) + ", " : "";
    andString = years + months ? "and " : "";
    daysString = "" + days + " day" + (s(days));
    return yearsString + monthsString + andString + daysString;
  };