Time Magic

Gather around, let me teach you some time magic (math). this time I'll teach you how to find the day of the week from a given date.
we will use this nice little chart with a lot of numbers. we will use the date February 8th 2021 as an example.
First you'll look at the hundreds, we have 20 so we look at the # column and write down 0 (if you're interested it goes by remainders of 4, 20 divided by 4 has a remainder of 0 so r0)
then you'll look at the remaining year digits, 21 in our case which corresponds to 5 in the # column so we write down 5.
then we have the month, we have February (non leap year) so we use the non green February and write down 3 (on leap years use the green February and January, leap years happen on year divisible by 4 unless they are divisible by 100 unless they are divisible by 400, if you don't want to calculate just look at the chart, if the year is in bold its a leap year, if it ends with 00 its not a leap year unless it also starts with bold numbers)
Now we take all the numbers we wrote down, 0, 5, 3 and add them up with the day of the month, in our case, 8. so 0+5+3+8=16 take that number and find the remainder to dividing by 7. 16 divided by 7 is 2 with a remainder of 2.
Now look at 2 in # column and look to what it corresponds in the DW (Day of Week) column (Sunday is 1 and Friday is 6, Saturday is 0).

Now you can calculate every date you want (gets funky for date before October 1582)

 

yes, much understand and looking at table, big like, cause lots of effort. Good math

 

Didnt you already post this months ago?

 

tbh maybe I lost track of what I did already