How do I disassemble the Oregon Scientific RM329PU (setting time zone)

There are no physical buttons to set the time zone for the radio-controlled clock. As a result, the clock automatically sets itself to Germany's time zone (since it receives the DCF77 time signal from Frankfurt). While I can manually adjust the time, I would appreciate finding a way to set the time zone.

I find it hard to believe this product was designed exclusively for the German time zone. I suspect this function can be adjusted directly through the electronic board, but I'm hesitant to disassemble the clock. There are only two visible screws in the battery unit, and removing them hasn't made any difference. Are all the parts clipped or glued together? Any suggestions on how to open it or adjust the time zone would be greatly appreciated. Thank you.