how to convert php date formats to GMT and vice versa?

Question

i am new to php. i want to write a function where i need user to input date in any date format including DST,into GMT format and again later back into the original entered format.please any body help me.

Answer 1

Although the gmdate functions are available. If you are using PHP 5.2 or greater, then consider using the DateTime object.

Here's code to switch to GMT

$date = new DateTime();
$date->setTimezone(new DateTimeZone('GMT'));

and back to the default timezone...

$date = new DateTime('2011-01-01', new DateTimeZone('GMT'));
$date->setTimezone(new DateTimeZone(date_default_timezone_get()));

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Using the DateTime object lets your create a datetime, just like the procedural functions, except that you keep a reference to an instance.

e.g.

// Get a reference to Christmas of 2011, at lunch time.
$date = new DateTime('2011-12-25 13:00:00');

// Print the date for people to see, in whatever format we specify.
echo $date->format('D jS M y');

// Change the timezone to GMT.
$date->setTimezone(new DateTimeZone('GMT'));

// Now print the date/time it would in the GMT timezone
// as opposed to the default timezone it was created with.
echo $date->format('Y-m-d H:i:s');

// Just to show of some more, get the previous Sunday
$date->modify('previous Sunday');

There's a whole lot of functions you can use, that are much more readable that the procedural functions.

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Explicit example of converting from a timezone to GMT

$melbourne = new DateTimeZone('Australia/Melbourne');
$gmt = new DateTimeZone('GMT');

$date = new DateTime('2011-12-25 00:00:00', $melbourne);
$date->setTimezone($gmt);
echo $date->format('Y-m-d H:i:s');
// Output: 2011-12-24 13:00:00
// At midnight on Christmas eve in Melbourne it will be 1pm on Christmas Eve GMT.

echo '<br/>';

// Convert it back to Australia/Melbourne
$date->setTimezone($melbourne);
echo $date->format('Y-m-d H:i:s');

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Using your Asia/Kolkata to America/New_York

date_default_timezone_set('Asia/Kolkata');
$date = new DateTime('2011-03-28 13:00:00');
$date->setTimezone(new DateTimeZone('America/New_York'));
echo $date->format("Y-m-d H:i:s");
//Outputs: 2011-03-28 03:30:00