SECSPERREPEAT
years = (time_t)(seconds / SECSPERREPEAT
newt = (time_t)(t + seconds + SECSPERREPEAT);
newt = (time_t)(t - seconds - SECSPERREPEAT);
#define AVGSECSPERYEAR (SECSPERREPEAT / YEARSPERREPEAT)
intmax_t sec = SECSPERREPEAT, result = cycles * sec;