Hello, Freethinkers
Back with answers to questions nobody asked, like what is a razor, but hopefully answers people can use.
Who's familiar with the easy way to determine the day of the week from the date? Well, it's easy for the year we're in if one knows that year's "doomsday" is Friday. If we know the date of one Friday per month, we can determine the days that go with the other days that month.
The mnemonic is 7-11 is open 9-5. 7/11, 11/7, 5/9, and 9/5 are all doomsdays every year.
For the even numbered months after February, it's even easier: 4/4, 6/6. 8/8, 10/10, and 12/12 are all doomsdays. This year, they are all Fridays. Next year, they are all Saturdays, in 2027, and they will all be Sundays (in 2028, the doomsday is a Tuesday).
Jan, Feb, and March have their own ad hoc rules.
To include Feb and March, remember that March 0 is a doomsday. This refers to the day before March 1, which varies from Feb 28 to Feb 29 depending on whether it's a leap year, and tells us that Mar 7 is also a doomsday.
January is also a one-off, Jan 3 and 4 being doomsdays according to whether the year is a leap year.
I've found this to be a handy trick to use.
So, let's apply this:
October 16 is a Thursday because 10/10 is a doomsday which is a Friday this year, and so 10/17 is also a Friday and 10/16 a Thursday. Easy peasy.
November 20 is also a Thursday because 11/7 is a doomsday, so 11/21 is also a Friday and 11/20 a Thursday.
What day of the week does Christmas fall on this year? 12/12 is a doomsday (Friday this year), so two weeks later, 12/26 will be a Friday, and Christmas will be on a Thursday. My birthday is 8/14. What day of the week will it be in 2026, when the doomsday is Saturday. 8/8 is a doomsday (Saturday in 2026), so 8/14/26 will be a Friday.
This link goes into more detail for those interested in learning how to do this for any year in any century in either the Julian or Gregorian calendars, which is really a lot of work to learn, but possibly interesting to read for some. What is the day of the week? There's not much practical value to knowing more than how to do the year you're in, or maybe the year before and after, which as we just saw, is fairly simple
| What is the day of the week? |
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Stephen