A recurring theme in the books of the late, great military historian John Keegan was that some spots in the world are so strategically important that these same places become the sites of important battles over and over again. For instance, the battles of Agincourt (1415); Waterloo (1815) and the Somme (1916) all happened in a relatively small chunk of northern France and Belgium. In North America, Lake Champlain (French and Indian War and American Revolution) and Yorktown (American Revolution and American Civil War) are two examples.

After Monday’s terrorist bombing at the Boston Marathon, I’m starting to wonder if there is a chronological corollary. In other words, is there a time of year that hosts a disproportionate share of violent events? My nominee is the week of April school vacation. This is not the same week each year, but it hovers around the middle of the month and for us here in Massachusetts, it tends to be anchored by the Patriots Day holiday. Consider this roster of events:

• April 14, 1865 – President Lincoln assassinated
• April 14, 1912 – RMS Titanic hits iceberg and sinks
• April 16, 2007 – Virginia Tech massacre; 32 dead
• April 17, 1961 – Bay of Pigs invasion
• April 18, 1983 – US Embassy in Lebanon bombed; 63 dead
• April 19, 1775 – Battles of Lexington and Concord
• April 19, 1861 – Baltimore Riot involving Lowell-based 6th Mass Infantry
• April 19, 1993 – Waco, Texas – Branch Davidian Compound burns
• April 19, 1995 – Oklahoma City Bombing; 168 dead
• April 20, 1999 – Columbine High School massacre; 13 dead

To this list we can now add “April 15, 2013 – Boston Marathon Bombing; 3 dead”