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k1ooo-slr-sales · ‎11-07-2023

A useful little thread to help you work out the day of the week (in your head) for any date this year, and next year, and the year after that . . . and so on . . . and you don't need to be a genius (I little know I am not).

I saw some YouTube vids some time back that show you how to calculate the day of the week for any day of any year without computers, mobile phones or any device, just your brain.

https://youtu.be/714LTMNJy5M

My head hurts trying to remember the calculations and trying to divide some big numbers by 4, 7 or 12 and know the remainder, so I worked out something that simplified it for me. You can do it in your head by remembering just a few things and being a little bit good at Maths.

I was at the doctors a couple of months ago and the receptionist said "you can have an appointment on the 18th July" and quick as a flash I replied "Tuesdays are good for me". She had a puzzled look on her face because I replied so quickly.

The idea of posting this today is because today is one of the 'special days' you will need to remember. Each month has one . . . and they are not too difficult to commit to memory. On one of the videos I saw they called it the 'doomsday' for the month.

If you know the day of the week for just one day each month, you can simply add/subtract 7 to help find all other days of the month.

The 'doomsday' for each month is the same day of the week in a year.

- for 2023 it is Tuesday

- 2024 it is Thursday

- 2025 is Friday

. . . and so on.

So the easiest way to remember this year's 12 doomsdays is in three parts.

Part one - X/X/2023

- 04/04/2023 is a Tuesday

- 06/06/2023 is a Tuesday

- 08/08, 10/10 & 12/12 are Tuesdays

That is 5 months taken care of.

Part two

Remember this little ditty

"Some people work nine til five at seven eleven"

- 09/05 & 05/09 are Tuesdays

- 07/11 & 11/07 are Tuesdays

That is 9 months taken care of.

Part three (Jan, Feb, March)

- Jan 4th in a leap year (every 4th year) will be a doomsday.

- for the three years before and after leap years it will be Jan 3rd.

- the last day of Feb, every year, will be a doomsday

- the USA write their dates as MM/DD/YYYY. So March 14th is written 3/14. This is celebrated in the Maths community as 'pi day' because 3.14 is an approximation of pi ( π ). March 14th is a doomsday.

Now you have a quick way to know the day of the week for one day each month.

For 2023, just add or subtract 7 to a doomsday to find all the Tuesdays for each month.

TODAY is the doomsday for July, so the (11-7=4th), 11th, (11+7=18th) & (18+7=25th) are all Tuesdays. From here you just work your way to the date you want

e.g. What day of the week is the 21st July (my brother in law's birthday)? 11+7=18th is Tuesday, 19 Wed, 20 Thurs, 21 Friday (you can do this last counting on your fingers 😀).

Once you work out a few 'days' you will get good at it. Start with the birthdays of family members, then other significant days like:

- Australia Day

- Valentines Day

- ANZAC Day

- Christmas & Boxing Day

- April Fool's Day

- Star Wars Day ("May the 4th be with you")

Once you get quick at doing this it can become a party trick, especially if someone asks you for the day their birthday falls and it happens to be a doomsday, you will be able to answer within seconds. Days either side of doomdays will also be able to be done in seconds.

k1ooo-slr-sales · ‎11-07-2023

Tricking kids, especially teens!

If you have kids, or grandkids, or nieces or nephews, you can show them how smart you are by doing this brain exercise for a date of their choosing and racing them to see who can be first to name the day.

If you ask a child to choose a date this year, they are likely to choose their birthday first, so have that worked out before performing the trick. Also know Christmas Day.

You can use stalling tactics when racing them in working out a day with them being able to use a mobile phone calendar to look up the date.

Let them choose a date, ask what it is, then tell them they have to lock screen the phone as they have too big an advantage. Then negotiate another person to say "Go" before they can unlock the mobile and navigate their way to the calendar. You will have bought yourself time to start working out the day while establishing the rules. With experience, you'll only need to 'buy' 10 seconds. As soon as you hear "Go" you say the day because you started working it out as soon as they nominated the date.

For a repeat contest, engage in some banter after they nominate a date, say something like “do you really think you can beat me this time?” or “let’s have a bet, loser has to give a back rub” or “loser has to wash the dishes”. They will catch on that you are buying time after you beat them a few times. But when you beat them the first few times they will be gobsmacked and will want to have another go.