For the past few months, I’ve been creating a calendar for our partners at Booking.com. Months? Yes, months. Creating a calendar that works correctly all across the world for 42 different languages and even more locales, is not something that you do in a week. In this talk, I will talk to you about the weird things I learned. From Brazilian Summer Time to Slovakian date formatting. And how to avoid the many (many!) mistakes I made.