Function add_minutes_to_datetimestruct

numpy/core/src/multiarray/datetime.c:2059–2091

* Adjusts a datetimestruct based on a minutes offset. Assumes * the current values are valid. */

 * the current values are valid.
 */
NPY_NO_EXPORT void
add_minutes_to_datetimestruct(npy_datetimestruct *dts, int minutes)
{
    int isleap;

    dts->min += minutes;

    /* propagate invalid minutes into hour and day changes */
    dts->hour += extract_unit_32(&dts->min,  60);
    dts->day  += extract_unit_32(&dts->hour, 24);

    /* propagate invalid days into month and year changes */
    if (dts->day < 1) {
        dts->month--;
        if (dts->month < 1) {
            dts->year--;
            dts->month = 12;
        }
        isleap = is_leapyear(dts->year);
        dts->day += _days_per_month_table[isleap][dts->month-1];
    }
    else if (dts->day > 28) {
        isleap = is_leapyear(dts->year);
        if (dts->day > _days_per_month_table[isleap][dts->month-1]) {
            dts->day -= _days_per_month_table[isleap][dts->month-1];
            dts->month++;
            if (dts->month > 12) {
                dts->year++;
                dts->month = 1;
            }
        }
    }
}

/*
 * Tests for and converts a Python datetime.datetime or datetime.date