Note that holidays are not only bound to countries. Here in Germany, we have 16 states with different holiday laws. For example, the 3th October is celebrated everywhere as the German Unity Day, but there are holidays specific to catholic or protestantic states, and some holidays are only celebrated in one or two states.
Scaling up to the whole world, one might have to handle holidays for some hundred or even thousand regions, but if you want to handle holidays, you will have to go through that.
About holidays
Note that holidays are not only bound to countries. Here in Germany, we have 16 states with different holiday laws. For example, the 3th October is celebrated everywhere as the German Unity Day, but there are holidays specific to catholic or protestantic states, and some holidays are only celebrated in one or two states.
Scaling up to the whole world, one might have to handle holidays for some hundred or even thousand regions, but if you want to handle holidays, you will have to go through that.