Javascript 仅使用php、html和vanila js将时区放在两个selects标记中

我想创建两个日期时区选择，因为我想计算两个日期时区之间的差异。我有owner类，现在我想把它们放在两个选项中，并以这种格式（Y-m-DH:m:s）打印它们

以下是PHP代码：

莫斯科
加德满都
大马士革
莫斯科
加德满都
大马士革

请查看PHP文档中的内容

下面是一个如何实现此结果的示例：

/**  Returns the offset from the origin timezone to the remote timezone, in seconds.
*    @param $remote_tz;
*    @param $origin_tz; If null the servers current timezone is used as the origin.
*    @return int;
*/
function get_timezone_offset($remote_tz, $origin_tz = null) {
    if($origin_tz === null) {
        if(!is_string($origin_tz = date_default_timezone_get())) {
            return false; // A UTC timestamp was returned -- bail out!
        }
    }
    $origin_dtz = new DateTimeZone($origin_tz);
    $remote_dtz = new DateTimeZone($remote_tz);
    $origin_dt = new DateTime("now", $origin_dtz);
    $remote_dt = new DateTime("now", $remote_dtz);
    $offset = $origin_dtz->getOffset($origin_dt) - $remote_dtz->getOffset($remote_dt);
    return $offset;
}

示例：

// This will calculate the difference. It returns 10800 (3 hours) ...
$offset = get_timezone_offset('America/Los_Angeles','America/New_York');
// or, if your server time is already set to 'America/New_York'...
$offset = get_timezone_offset('America/Los_Angeles');
// You can then take $offset and adjust your timestamp.
$offset_time = time() + $offset;

// To display the formatted time
echo date('Y-m-d h:m:s', $offset_time);

// This will calculate the difference. It returns 10800 (3 hours) ...
$offset = get_timezone_offset('America/Los_Angeles','America/New_York');
// or, if your server time is already set to 'America/New_York'...
$offset = get_timezone_offset('America/Los_Angeles');
// You can then take $offset and adjust your timestamp.
$offset_time = time() + $offset;

// To display the formatted time
echo date('Y-m-d h:m:s', $offset_time);