Function utoff_diff

localtime.c:2548–2553

Return A - B, where both are in the range -2**31 + 1 .. 2**31 - 1. The result cannot overflow. */

	yourtm.tm_min = min % MINSPERHOUR;
	if (yourtm.tm_min < 0) {
	  yourtm.tm_min += MINSPERHOUR;
	  hour--;
	}

	mday = yourtm.tm_mday;
	mday += hour / HOURSPERDAY;
	yourtm.tm_hour = hour % HOURSPERDAY;
	if (yourtm.tm_hour < 0) {
	  yourtm.tm_hour += HOURSPERDAY;