code: function compare(aOther) {
        var thisSeconds = this.toSeconds();
        var otherSeconds = aOther.toSeconds();
        return (thisSeconds > otherSeconds) - (thisSeconds < otherSeconds);
      }
docs: Compares the duration instance with another one.
  
  @param {ICAL.Duration} aOther        The instance to compare with
  @return {Number}                     -1, 0 or 1 for less/equal/greater