adjhour
if (!adjhour(t, '+', (t->tm_min + val) / 60, 0))
if (!adjhour(t, '-', val / 60, 0))
if (!adjhour(t, '-', 1, 0))
if (!adjhour(t, type, val, 1))
static int adjhour(struct tm *, char, int64_t, int);
adjhour(t, type == '-' ? type : '+', 1, 0);