Function make_iso_8601_datetime

numpy/core/src/multiarray/datetime_strings.c:886–1327

* Converts an npy_datetimestruct to an (almost) ISO 8601 * NULL-terminated string. If the string fits in the space exactly, * it leaves out the NULL terminator and returns success. * * The differences from ISO 8601 are the 'NaT' string, and * the number of year digits is >= 4 instead of strictly 4. * * If 'local' is non-zero, it produces a string in local time with * a +-#### timezone offs

 *  string was too short).
 */
NPY_NO_EXPORT int
make_iso_8601_datetime(npy_datetimestruct *dts, char *outstr, npy_intp outlen,
                    int local, int utc, NPY_DATETIMEUNIT base, int tzoffset,
                    NPY_CASTING casting)
{
    npy_datetimestruct dts_local;
    int timezone_offset = 0;

    char *substr = outstr;
    npy_intp sublen = outlen;
    npy_intp tmplen;

    /* Handle NaT, and treat a datetime with generic units as NaT */
    if (dts->year == NPY_DATETIME_NAT || base == NPY_FR_GENERIC) {
        if (outlen < 3) {
            goto string_too_short;
        }
        outstr[0] = 'N';
        outstr[1] = 'a';
        outstr[2] = 'T';
        if (outlen > 3) {
            outstr[3] = '\0';
        }

        return 0;
    }

    /*
     * Only do local time within a reasonable year range. The years
     * earlier than 1970 are not made local, because the Windows API
     * raises an error when they are attempted (see the comments above the
     * get_localtime() function). For consistency, this
     * restriction is applied to all platforms.
     *
     * Note that this only affects how the datetime becomes a string.
     * The result is still completely unambiguous, it only means
     * that datetimes outside this range will not include a time zone
     * when they are printed.
     */
    if ((dts->year < 1970 || dts->year >= 10000) && tzoffset == -1) {
        local = 0;
    }

    /* Automatically detect a good unit */
    if (base == NPY_FR_ERROR) {
        base = lossless_unit_from_datetimestruct(dts);
        /*
         * If there's a timezone, use at least minutes precision,
         * and never split up hours and minutes by default
         */
        if ((base < NPY_FR_m && local) || base == NPY_FR_h) {
            base = NPY_FR_m;
        }
        /* Don't split up dates by default */
        else if (base < NPY_FR_D) {
            base = NPY_FR_D;
        }
    }