Warning when people place preorder in different time zone

Please put a warning when people place preorder in different time zone - have had customers place an order a few days in advance whilst still on their holiday and it books them into the slot 1 or 2 hours earlier..! (If they are in Spain and book 8pm, it actually books them into the 7pm slot - maybe make sure preorder slots are in the restaurant's time zone, not that of the customer!)