code: function icaltime_compareDateOnlyTz(other, tz) {
        function cmp(attr) {
          return ICAL.Time._cmp_attr(a, b, attr);
        }
        var a = this.convertToZone(tz);
        var b = other.convertToZone(tz);
        var rc = 0;
  
        if ((rc = cmp("year")) != 0) return rc;
        if ((rc = cmp("month")) != 0) return rc;
        if ((rc = cmp("day")) != 0) return rc;
  
        return rc;
      }
docs: Compares only the date part of this instance with another one.
  
  @param {ICAL.Duration} other         The instance to compare with
  @param {ICAL.Timezone} tz            The timezone to compare in
  @return {Number}                     -1, 0 or 1 for less/equal/greater