Take 10 minutes and think about the following:

• I am French, born in NYC the 24th of April at 3pm. What is my birth date on my passport?
• If was living in Thailand and wanted to open a bank account what birth date should I give (Hint: Thailand does not use the Gregorian calendar) ?
• I want a job to be scheduled for execution every Sundays at 2:30am
• I am in Durban (Australia) and I want to see all operations made in London yesterday.

If you don’t see any challenge you’d better not be coding for an application with geographically distributed users ;)