This is the Calendar for the Year 2025
[ 255 136 140 250 ]
And…? Well, that’s all of it.
If you can memorize that number (just like you memorize any phone number), and if you can do a simple calculation, You will be able to find instantly, the weekday that a date falls on.
Now let’s understand the calendar, in two Steps.
Before starting, first understand that each of these 12 digits corresponds to the months of the year 2025. Lets call them the Month’s Tag Numbers.
255 136 140 250
Jan-2 Feb-5 Mar-5, Apr-1 May-3 Jun-6, Jul-1 Aug-4 Sep-0, Oct-2 Nov-5 Dec-0.
Also know the WeekDay Numbers , starting from Monday; Monday = 1 being the first day of the week.
Mon=1, Tue=2, Wed=3. Thu=4, Fri=5, Sat=6, Sun=7 or 0.
- Step-1. Add the Date and Month Tag
For eg., For 15th August, The Tag of August ( See Above) is 4, and the Date is 15.
Add 15(date) + 4(Aug tag) =19 - Step-2. Strip out the weeks
From 19, stripout or remove the maximum weeks you can
19-14(or 2 weeks) =5. - This is the Answer: Day no. 5 of the week is Friday for 15 August 2025
Another example
Lets try Another, say, 25 Dec Xmas.
(Date 25+Dec Tag 0 ) = 25. 25 stripped (25-21) is 4. The 4th day of the week is Thursday.
You will soon find this works in a fraction of a second; faster than picking up the phone or turning the calendar page.
Have Fun!
For the calculative and curious- how it works
We know that the Calendar, though the most important productivity basic tool, is not really the most scientific of things.
So let us imagine an Ideal World Calendar, where every weekday of every month will always fall on the same day. ie,.
Mon=1, Tue=2, Wed=3. Thu=4, Fri=5, Sat=6, Sun=7 or 0., and so on.
Now lets compare the Month of January 2025.
You will notice that to convert the Ideal Calendar Month to January, you need to Push it 2 days forward. So that the month now starts on Wed instead of Mon. That Deviance or Difference = 2 days, or as we may call it the Tag number for the month of January.
The math inclined will also notice that the month Tag can also be calculated by: 7 minus (the date of the first Sunday of the month Jan). i.e 7-5=2.
Similarly you can get the Deviance or Tag numbers of all the months, to give you the Calendar of the year.
An example
So for eg., to check out 26th of January, On the Ideal World Calendar, the 26th date would fall on (26 = 21+ 5), ie (3weeks + the 5th day), which is Friday. For January 2025, we push this 5th day, 2 days forward, to get Sunday. which is Day 7 or 0.
So the easier Calculation is to Add date and Discrepancy, 26+2=28. Strip out weeks and its a Sunday.
A Memory Hack
Usually when I start the year, I paste a sticker with the number somewhere where I can instantly see it. Over a short time, it gets memorized without effort. Also, the Tag number of the current month and the next is the most used. So start with these 2 numbers.
QED.
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