DAYSPERREPEAT
dayrem = (int)(tdays % DAYSPERREPEAT);
dayrem += dayoff % DAYSPERREPEAT;
+ ((1 + dayoff / DAYSPERREPEAT + dayrem / DAYSPERREPEAT
- ((dayrem % DAYSPERREPEAT) < 0)
+ tdays / DAYSPERREPEAT)
idays = (int)(tdays % DAYSPERREPEAT);
idays += (dayoff % DAYSPERREPEAT + 2 * DAYSPERREPEAT);
idays %= DAYSPERREPEAT;
#define SECSPERREPEAT ((int_fast64_t) DAYSPERREPEAT * SECSPERDAY)
DAYSPERREPEAT);