typedef struct {
    uint8_t sec;
    uint8_t min;
    uint8_t hour;
    uint8_t day;
    uint8_t month;
    uint64_t year;
} human_time_t;

//Needs to be converted to time_t

/* returns the GDN of January 1 of a given year */
int year_to_gdn(int year, int *is_leap) {
  /* year is the Gregorian calendar year */
  assert(year >= 1); /* C integer math with negative numbers is weird. And you don't really work with Roman times, right? */
  assert(year < INT_MAX/146097); /* otherwise this overflows the calculation down there */
  year--; /* makes the upcoming calculations easier */
  int cycle = year / 400;
  int year_in_cycle = year % 400;
  int century = year_in_cycle / 100;
  int year_in_century = year_in_cycle % 100;
  int group = year_in_century / 4;
  int year_in_group = year_in_century % 4;
  if (is_leap) *is_leap = year_in_group == 3 && (year_in_century != 99 || year_in_cycle == 399);
  return 146097 * cycle + 36524 * century + 1461 * group + 365* year_in_group;
}

int tm_to_gdn(const struct tm *tm) {
  int is_leap;
  static const unsigned short month_to_gdn[12] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
  int gdn = year_to_gdn(tm->tm_year + 1900, &is_leap);
  gdn += month_to_gdn[tm->tm_mon] + (is_leap && tm->tm_mon > 1);
  gdn += tm->tm_mday - 1;
  return gdn;
}

#define GDN_EPOCH 719162

time_t tm_to_time(const struct tm *tm) {
  int gdn = tm_to_gdn(tm);
  return (gdn - GDN_EPOCH) * 86400LL + tm->tm_hour * 3600 + tm->tm_min * 60 + tm->tm_sec;
}