I've searched all over including a few threads here on this topic and it looks like I'm running out of options. I'm developing a travel reservations website with a promotional code field on the payment page. The admin wants to be able to create coupon codes with an expiry date. How do I check the expiry date of the coupon against the user's local time with a server side language like php? My server's timezone is CST but the reservations come form all over the world.
Or any other possible way to approach the expiring coupon problem would be appreciated as well.