如果您没有将日期传递给wp_insert_post(), get_gmt_from_date() 被调用。看看这个函数的内容：

function get_gmt_from_date($string, $format = \'Y-m-d H:i:s\') {
    preg_match(\'#([0-9]{1,4})-([0-9]{1,2})-([0-9]{1,2}) ([0-9]{1,2}):([0-9]{1,2}):([0-9]{1,2})#\', $string, $matches);
    if ( ! $matches )
        return date( $format, 0 );

    $tz = get_option(\'timezone_string\');
    if ( $tz ) {
        date_default_timezone_set( $tz );
        $datetime = date_create( $string );
        if ( ! $datetime )
            return date( $format, 0 );

        $datetime->setTimezone( new DateTimeZone(\'UTC\') );
        $offset = $datetime->getOffset();
        $datetime->modify( \'+\' . $offset / HOUR_IN_SECONDS . \' hours\');
        $string_gmt = gmdate($format, $datetime->format(\'U\'));

        date_default_timezone_set(\'UTC\');
    } else {
        $string_time = gmmktime($matches[4], $matches[5], $matches[6], $matches[2], $matches[3], $matches[1]);
        $string_gmt = gmdate($format, $string_time - get_option(\'gmt_offset\') * HOUR_IN_SECONDS);
    }
    return $string_gmt;
}