Question

My task: I am going to run a contest world wide at my website. A problem setter will set problems from a specific area of the world setting a time and date of starting time of the contest. I have to show that time correctly all over the world so the the contest starts at a time everywhere of the world.
My Idea : I planed to get the time from the problem setter of his time zone using server site language like php time(), & will store to database converting to timezone= zero (0). And who are going to attend the contest I’ll just add hour(s) of that time zone with my database time.

Need help: I have no Idea how to convert that timestamps to timezone ‘zero’, even how can I get the ±hour(s) of current timezone?
Thank you…

Answer 1

Step 1:
Let the user choose his timezone. You could fill a dropdown with values from this site: http://php.net/manual/en/timezones.php

Step 2:
Convert the timezone to servertime

$timezone_client = new DateTimeZone('America/Denver');
$timezone_server = new DateTimeZone('Pacific/Nauru');
$datetime = new DateTime('2013-01-25 12:00:00', timezone_client);
$datetime->setTimezone($timezone_server);
echo $datetime->format('Y-m-d H:i:s');