func commonTime(modTimes []time.Time, quorum int) time.Time {
	if modTime, count := commonTimeAndOccurrence(modTimes, 0); count >= quorum {
		return modTime
	}

	return timeSentinel
}

func commonETag(etags []string, quorum int) string {
	if etag, count := commonETags(etags); count >= quorum {
		return etag
	}
	return ""
}

// Beginning of unix time is treated as sentinel value here.
var (