Function cast_datetime_to_datetime

numpy/core/src/multiarray/datetime.c:3012–3038

* Casts a single datetime from having src_meta metadata into * dst_meta metadata. * * Returns 0 on success, -1 on failure. */

 * Returns 0 on success, -1 on failure.
 */
NPY_NO_EXPORT int
cast_datetime_to_datetime(PyArray_DatetimeMetaData *src_meta,
                          PyArray_DatetimeMetaData *dst_meta,
                          npy_datetime src_dt,
                          npy_datetime *dst_dt)
{
    npy_datetimestruct dts;

    /* If the metadata is the same, short-circuit the conversion */
    if (src_meta->base == dst_meta->base &&
            src_meta->num == dst_meta->num) {
        *dst_dt = src_dt;
        return 0;
    }

    /* Otherwise convert through a datetimestruct */
    if (convert_datetime_to_datetimestruct(src_meta, src_dt, &dts) < 0) {
            *dst_dt = NPY_DATETIME_NAT;
            return -1;
    }
    if (convert_datetimestruct_to_datetime(dst_meta, &dts, dst_dt) < 0) {
        *dst_dt = NPY_DATETIME_NAT;
        return -1;
    }

    return 0;
}

/*
 * Casts a single timedelta from having src_meta metadata into