code: function startOfWeek(aWeekStart) {
        var firstDow = aWeekStart || ICAL.Time.SUNDAY;
        var result = this.clone();
        result.day -= ((this.dayOfWeek() + 7 - firstDow) % 7);
        result.isDate = true;
        result.hour = 0;
        result.minute = 0;
        result.second = 0;
        return result;
      }
docs: Returns a copy of the current date/time, rewound to the start of the
  week. The resulting ICAL.Time instance is of icaltype date, even if this
  is a date-time.
  
  @param {ICAL.Time.weekDay=} aWeekStart
  The week start weekday, defaults to SUNDAY
  @return {ICAL.Time}      The start of the week (cloned)