Doomsdays

Doomsdays

Every year, a set of easy-to-remember dates all land on the same weekday as each other. The next thing to learn is that set — a handful of dates, spread through the year, all sharing one weekday.

The dates we are about to learn are called doomsdays.

In all the even months, apart from the special month of February, the doomsday is the same as the month number.

Remembering the phrase I work at 7-Eleven from 9 to 5 makes four more doomsdays easy to recall. Its numbers — 9, 5, 7 and 11 — pair up as month and day in both directions: 5 September and 9 May, 11 July and 7 November.

The remaining three months are the first three of the year:

The doomsday in January depends on whether the year is a leap year. In the three common years of the cycle it is the 3rd, and in the leap year itself it is the 4th.

In February, we simply need to remember that the last day of the month is a doomsday. In a common year that is the 28th; in a leap year it is the 29th.

Since February is the month leading up to March, some people find it easier to remember the doomsday in February as the 0th day of March. This is the day before the first day. It also means you can use the 7th, 14th, 21st and 28th — the multiples of 7 — as doomsdays in March.

Here you can see that every doomsday in 2024 falls on a Thursday:

Those are the doomsday dates, and they never change. What changes is which weekday they share — that depends on the year, and working it out is the next section. From there, any date is a short count away from its nearest doomsday.