Same in Germany, Spick. On your birthday you have completed your 39th and are in the 40th - just get used to it <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
Kiya

It's logical, you don't celebrate your 1st birhtday on the day of your birth, do you? No, you celebrate your successful completion of the current one.