Function is_leapyear

numpy/core/src/multiarray/datetime.c:109–115

* Returns 1 if the given year is a leap year, 0 otherwise. */

 * Returns 1 if the given year is a leap year, 0 otherwise.
 */
NPY_NO_EXPORT int
is_leapyear(npy_int64 year)
{
    return (year & 0x3) == 0 && /* year % 4 == 0 */
           ((year % 100) != 0 ||
            (year % 400) == 0);
}

/*
 * Calculates the days offset from the 1970 epoch.