It's a pain in the ass isn't it? It's especially annoying when you employ people in multiple countries, you never know when the holidays are and everyone assumes that you know... they simply don't show up for work and you have to call someone at home to figure out why nobody is taking calls at the office...
Spring is the worst, what gets me about these religious holidays is that otherwise satanic heavy metal listening porn lovers who despise anything religious feel it's their birthright not to work on days like good Friday etc. while they don't even know what the holiday is about in the first place.