php 1970年前日期问题

function smarty_make_timestamp($string)
{
    if(empty($string)) {
        // use "now":
        $time = time();

    } elseif (preg_match('/^\d{14}$/', $string)) {
        // it is mysql timestamp format of YYYYMMDDHHMMSS?           
        $time = mktime(substr($string, 8, 2),substr($string, 10, 2),substr($string, 12, 2),
                       substr($string, 4, 2),substr($string, 6, 2),substr($string, 0, 4));
       
    } elseif (is_numeric($string)) {
        // it is a numeric string, we handle it as timestamp
        $time = (int)$string;
       
    } else {
        // strtotime should handle it
        $time = strtotime($string);
        if ($time == -1 || $time === false) {
            // strtotime() was not able to parse $string, use "now":
            $time = time();
        }
    }
    return $time;

}

function smarty_modifier_date_format($string, $format = '%Y-%m-%d %H:%M:%S ', $default_date = '')
{
    if ($string != '') {
        $timestamp = smarty_make_timestamp($string);
    } elseif ($default_date != '') {
        $timestamp = smarty_make_timestamp($default_date);
    } else {
        return;
    }
    if (DIRECTORY_SEPARATOR == '\\') {
        $_win_from = array('%D',       '%h', '%n', '%r',          '%R',    '%t', '%T');
        $_win_to   = array('%m/%d/%y', '%b', "\n", '%I:%M:%S %p', '%H:%M', "\t", '%H:%M:%S');
        if (strpos($format, '%e') !== false) {
            $_win_from[] = '%e';
            $_win_to[]   = sprintf('%\' 2d', date('j', $timestamp));
        }
        if (strpos($format, '%l') !== false) {
            $_win_from[] = '%l';
            $_win_to[]   = sprintf('%\' 2d', date('h', $timestamp));
        }
        $format = str_replace($_win_from, $_win_to, $format);
    }
    return strftime($format, $timestamp);
}

$sd1 = strtotime("1802-10-12");
echo $sd1.'|| ';

$sd = smarty_make_timestamp("1905-10-12");
echo $sd.'|| ';
echo date("Y-m-d",$sd).'|| ';

echo smarty_modifier_date_format($sd);