src/time/__year_to_secs.c

   1 long long __year_to_secs(long long year, int *is_leap)
   2 {
   3         if (year-2ULL <= 136) {
   4                 int y = year;
   5                 int leaps = (y-68)>>2;
   6                 if (!((y-68)&3)) {
   7                         leaps--;
   8                         if (is_leap) *is_leap = 1;
   9                 } else if (is_leap) *is_leap = 0;
  10                 return 31536000*(y-70) + 86400*leaps;
  11         }
  12
  13         int cycles, centuries, leaps, rem;
  14
  15         if (!is_leap) is_leap = &(int){0};
  16         cycles = (year-100) / 400;
  17         rem = (year-100) % 400;
  18         if (rem < 0) {
  19                 cycles--;
  20                 rem += 400;
  21         }
  22         if (!rem) {
  23                 *is_leap = 1;
  24                 centuries = 0;
  25                 leaps = 0;
  26         } else {
  27                 if (rem >= 200) {
  28                         if (rem >= 300) centuries = 3, rem -= 300;
  29                         else centuries = 2, rem -= 200;
  30                 } else {
  31                         if (rem >= 100) centuries = 1, rem -= 100;
  32                         else centuries = 0;
  33                 }
  34                 if (!rem) {
  35                         *is_leap = 0;
  36                         leaps = 0;
  37                 } else {
  38                         leaps = rem / 4U;
  39                         rem %= 4U;
  40                         *is_leap = !rem;
  41                 }
  42         }
  43
  44         leaps += 97*cycles + 24*centuries - *is_leap;
  45
  46         return (year-100) * 31536000LL + leaps * 86400LL + 946684800 + 86400;
  47 }