I’ve always heard of doomsday referring to the end of the world. I’ve even heard it referring to comic book characters (notably Dr. Doom’s own holiday, Doom’s Day). I hadn’t known it was something that happened more than fifty times a year.

If you look at the calendar for this year, you’ll see that the 4th of April, the 6th of June, the 8th of August, the 10th of October, and the 12th of December all fall on the same day of the week: Tuesday. That’s 4/4, 6/6, 8/8, 10/10, and 12/12 — along with the dates 5/9, 7/11, 9/5, and 11/7. Pretty cool, huh?

Well, it’s not unique to 2017. It happens every year — those dates always fall on the same day relative to each other within any given year. This is called the Doomsday Rule, a clever way of mentally calculating the day of the week for any given date in any given year. Each year, the day of the week the above dates occur on is known as that year’s Doomsday. Other dates to remember are that Christmas and September 11th are always the day before Doomsday, and both the Fourth of July and Halloween are Doomsdays. Take what symbolism you wish from that.

One of the dates that always falls on a given year’s doomsday is the last day in February, which of course changes on every fourth year. If you notice, that means that three years out of every four, February 14th falls on that year’s doomsday.

That’s right, men. Watch out. For the next three years, St. Valentine’s Day is DOOMSDAY.

Doom.