[php] php convert datetime to UTC

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.

alternatively you can try this:

<?php echo (new DateTime("now", new DateTimeZone('Asia/Singapore')))->format("Y-m-d H:i:s e"); ?>

this will output :

2017-10-25 17:13:20 Asia/Singapore

you can use this inside the value attribute of a text input box if you only want to display a read-only date.

remove the 'e' if you do not wish to show your region/country.

try

echo date('F d Y', strtotime('2010-01-19 00:00:00'));

will output:

January 19 2010

you should change format time to see other output

Convert local time zone string to UTC string.
e.g. New Zealand Time Zone

$datetime = "2016-02-01 00:00:01";
$given = new DateTime($datetime, new DateTimeZone("Pacific/Auckland"));
$given->setTimezone(new DateTimeZone("UTC"));
$output = $given->format("Y-m-d H:i:s"); 
echo ($output);

• NZDT: UTC+13:00
  if $datetime = "2016-02-01 00:00:01", $output = "2016-01-31 11:00:01";
  if $datetime = "2016-02-29 23:59:59", $output = "2016-02-29 10:59:59";
  
• NZST: UTC+12:00
  if $datetime = "2016-05-01 00:00:01", $output = "2016-04-30 12:00:01";
  if $datetime = "2016-05-31 23:59:59", $output = "2016-05-31 11:59:59";
  

https://en.wikipedia.org/wiki/Time_in_New_Zealand

As an improvement on Phill Pafford's answer (I did not understand his 'Y-d-mTG:i:sz' and he suggested to revert timezone). So I propose this (I complicated by changing the HMTL format in plain/text...):

<?php
header('content-type: text/plain;');
$my_timestamp = strtotime("2010-01-19 00:00:00");

// stores timezone
$my_timezone = date_default_timezone_get();
echo date(DATE_ATOM, $my_timestamp)."\t ($my_timezone date)\n";

// changes timezone
date_default_timezone_set("UTC");
echo date("Y-m-d\TH:i:s\Z", $my_timestamp)."\t\t (ISO8601 UTC date)\n";
echo date("Y-m-d H:i:s", $my_timestamp)."\t\t (your UTC date)\n";

// reverts change
date_default_timezone_set($my_timezone);
echo date(DATE_ATOM, $my_timestamp)."\t ($my_timezone date is back)\n"; 
?>

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

If you don't mind using PHP's DateTime class, which has been available since PHP 5.2.0, then there are several scenarios that might fit your situation:

1. If you have a $givenDt DateTime object that you want to convert to UTC then this will convert it to UTC:

   $givenDt->setTimezone(new DateTimeZone('UTC'));
   

2. If you need the original $givenDt later, you might alternatively want to clone the given DateTime object before conversion of the cloned object:

   $utcDt = clone $givenDt;
   $utcDt->setTimezone(new DateTimeZone('UTC'));
   

3. If you only have a datetime string, e.g. $givenStr = '2018-12-17 10:47:12', then you first create a datetime object, and then convert it. Note this assumes that $givenStr is in PHP's configured timezone.

   $utcDt = (new DateTime($givenStr))->setTimezone(new DateTimeZone('UTC'));
   

4. If the given datetime string is in some timezone different from the one in your PHP configuration, then create the datetime object by supplying the correct timezone (see the list of timezones PHP supports). In this example we assume the local timezone in Amsterdam:

   $givenDt = new DateTime($givenStr, new DateTimeZone('Europe/Amsterdam'));
   $givenDt->setTimezone(new DateTimeZone('UTC'));
   

Do this way:

gmdate('Y-m-d H:i:s', $timestamp)

or simply

gmdate('Y-m-d H:i:s')

to get "NOW" in UTC.

Check the reference:

http://www.php.net/manual/en/function.gmdate.php

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)
   

As strtotime requires specific input format, DateTime::createFromFormat could be used (php 5.3+ is required)

// set timezone to user timezone
date_default_timezone_set($str_user_timezone);

// create date object using any given format
$date = DateTime::createFromFormat($str_user_dateformat, $str_user_datetime);

// convert given datetime to safe format for strtotime
$str_user_datetime = $date->format('Y-m-d H:i:s');

// convert to UTC
$str_UTC_datetime = gmdate($str_server_dateformat, strtotime($str_user_datetime));

// return timezone to server default
date_default_timezone_set($str_server_timezone);

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'));

I sometime use this method:

// It is not importnat what timezone your system is set to.
// Get the UTC offset in seconds:
$offset = date("Z");

// Then subtract if from your original timestamp:
$utc_time = date("Y-m-d H:i:s", strtotime($original_time." -".$offset." Seconds"));

Works all MOST of the time.

If you have a date in this format YYYY-MM-HH dd:mm:ss, you can actually trick php by adding a UTC at the end of your "datetime string" and use strtotime to convert it.

date_default_timezone_set('Europe/Stockholm');
print date('Y-m-d H:i:s',strtotime("2009-01-01 12:00"." UTC"))."\n";
print date('Y-m-d H:i:s',strtotime("2009-06-01 12:00"." UTC"))."\n";

This will print this:

2009-01-01 13:00:00
2009-06-01 14:00:00

And as you can see it takes care of the daylight savings time problem as well.

A little strange way to solve it.... :)

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

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"

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