Changing to Standard Time – How can you tell which hour?

It's time to change the clock tonight, meaning there will be 2x the same hour depending where you are.
Let's Alassuming the clock changes at 03.00, which means 02.00 to 02.59 will happen twice tonight. How do you know, if your boarding pass says 02.30, whether it is the 02.30 before or after the clock change?