code: func withinTimePeriod(start, end, now time.Time) bool {
  	// Converts to UTC and only keeps the hour and minute info.
  	start, end, now = start.UTC(), end.UTC(), now.UTC()
  	start = time.Date(0, 0, 0, start.Hour(), start.Minute(), 0, 0, time.UTC)
  	end = time.Date(0, 0, 0, end.Hour(), end.Minute(), 0, 0, time.UTC)
  	now = time.Date(0, 0, 0, now.Hour(), now.Minute(), 0, 0, time.UTC)
  	// for cases like from 00:00 to 06:00
  	if end.Sub(start) >= 0 {
  		return now.Sub(start) >= 0 && now.Sub(end) <= 0
  	}
  	// for cases like from 22:00 to 06:00
  	return now.Sub(end) <= 0 || now.Sub(start) >= 0
  }
docs: // withinTimePeriod tests whether `now` is between `start` and `end`.