Death and taxes are the only sure things, they say. The Ides of March - the 15th - is well-known as the day some folks got all stabby with Julius Caesar in 44 BC, an event (at least in Shakespeare's telling) predicted by a seer who was ignored by Caesar. April 15 is well-known as the due date for filing US Federal taxes. But as catchy as it would be to call tax day "the Ides of April" it is not. The Ides of April falls on the 13th. I won't bore you with the details of the Roman calendar; the simplest and yet still largely correct explaination is that the Ides of April is on the 13th because April has only 30 days, and the Ides of March is the 15th because March hath 31 days.
This year, April 15 is also Patriots' Day (commemorating first battles of the revolutionary way at Lexington and Concord) and Marathon Monday (the running of the Boston Marathon, commemorating in a roundabout way the Battle of Marathon in 490 BC, thereby predating Ceasar's assassination by a few hundred years) in Massachusetts, a state holiday for many. It's observed on the third Monday of March so it doesn't often align with the Ides or tax day, but this year it means that Massachusetts folk have an extra day to file their state taxes, though they still owe the feds today. You can confuse Patriots' Day in Massachusetts with Patriot's Day in Maine, (at the time of the events in question, they were the same state but I guess Maine got only one patriot in the breakup) but don't mix it up with Patriot Day on September 11.