php convert datetime to UTC

Question

I am in need of an easy way to convert a date time stamp to UTC (from whatever timezone the server is in) HOPEFULLY without using any libraries.

Answer 1

General purpose normalisation function to format any timestamp from any timezone to other. Very useful for storing datetimestamps of users from different timezones in a relational database. For database comparisons store timestamp as UTC and use with gmdate('Y-m-d H:i:s')

/**
 * Convert Datetime from any given olsonzone to other.
 * @return datetime in user specified format
 */

function datetimeconv($datetime, $from, $to)
{
    try {
        if ($from['localeFormat'] != 'Y-m-d H:i:s') {
            $datetime = DateTime::createFromFormat($from['localeFormat'], $datetime)->format('Y-m-d H:i:s');
        }
        $datetime = new DateTime($datetime, new DateTimeZone($from['olsonZone']));
        $datetime->setTimeZone(new DateTimeZone($to['olsonZone']));
        return $datetime->format($to['localeFormat']);
    } catch (\Exception $e) {
        return null;
    }
}

Usage:

$from = ['localeFormat' => "d/m/Y H:i A", 'olsonZone' => 'Asia/Calcutta'];

$to = ['localeFormat' => "Y-m-d H:i:s", 'olsonZone' => 'UTC'];

datetimeconv("14/05/1986 10:45 PM", $from, $to); // returns "1986-05-14 17:15:00"

Answer 2

Use strtotime to generate a timestamp from the given string (interpreted as local time) and use gmdate to get it as a formatted UTC date back.

Example

As requested, here’s a simple example:

echo gmdate('d.m.Y H:i', strtotime('2012-06-28 23:55'));

Answer 3

With PHP 5 or superior, you may use datetime::format function (see documentation http://us.php.net/manual/en/datetime.format.php)

 echo strftime( '%e %B %Y' , 
    date_create_from_format('Y-d-m G:i:s', '2012-04-05 11:55:21')->format('U')
    );  // 4 May 2012

Answer 4

Using DateTime:

$given = new DateTime("2014-12-12 14:18:00");
echo $given->format("Y-m-d H:i:s e") . "\n"; // 2014-12-12 14:18:00 Asia/Bangkok

$given->setTimezone(new DateTimeZone("UTC"));
echo $given->format("Y-m-d H:i:s e") . "\n"; // 2014-12-12 07:18:00 UTC

Answer 5

Follow these steps to get UTC time of any timezone set in user's local system (This will be required for web applications to save different timezones to UTC):

1. Javascript (client-side):

   var dateVar = new Date();
   var offset = dateVar.getTimezoneOffset();
   //getTimezoneOffset - returns the timezone difference between UTC and Local Time
   document.cookie = "offset="+offset;
   

2. Php (server-side):

   public function convert_utc_time($date)
   {
       $time_difference = isset($_COOKIE['offset'])?$_COOKIE['offset']:'';
       if($time_difference != ''){
           $time = strtotime($date);
           $time = $time + ($time_difference*60); //minutes * 60 seconds
           $date = date("Y-m-d H:i:s", $time);
       } //on failure of js, default timezone is set as UTC below
       return $date;
   }
   ..
   ..
   //in my function
   $timezone = 'UTC';
   $date = $this->convert_utc_time($post_date); //$post_date('Y-m-d H:i:s')
   echo strtotime($date. ' '. $timezone)
   

Answer 6

http://php.net/manual/en/function.strtotime.php or if you need to not use a string but time components instead, then http://us.php.net/manual/en/function.mktime.php