'Coincidentally, it is the same day as St. Patrick's Day'
Wikipedia provides a rather strange explanation about how Evacuation Day became a holiday in Massachusetts:
Many of the soldiers who volunteered to serve under General George Washington to break the yoke of British colonialism were Irish Catholic. These soldiers and their families experienced first hand British occupation and suppression. Many of their sacrifices during the War of Independence were critical in bringing about the establishment of the United States of America. After a failed movement in 1876, the holiday (Evacuation Day) was finally proclaimed on the 125th anniversary in 1901.
I get the distinct impression someone is trying too hard to rationalize the historic connection between Evacuation Day and St. Patrick's Day. ...
J.L. Bell, typically, has an interesting post on the real evacuation of Boston. No mention of Irish-Catholic minutemen hot on the heels of the fleeing Gen. William Howe. ...