leapyear
register bool leapyear;
leapyear = isleap(year);
if (leapyear && rulep->r_day >= 60)
mon_lengths[leapyear][rulep->r_mon - 1])
value += mon_lengths[leapyear][i] * SECSPERDAY;
rt->leapyear = dt->dt_year; /* XXX implicit % 4 */