What Day Is It?

Hello there! So after I made my Bored thread a lot of you voted on the poll that you wanted some cool maths and random knowledge. So today I'm gonna teach you how to know what day of the week it is.

First of all lets state what we know:
we're using the Gregorian calendar which you all know and love.
that means we have a 365 day long year (366 on leap years)
12 months with a length ranging between 28-31 days (short and long months always alternating

Spoiler: how to remember which months are long

hold your two fists closed next to each other, know you can count on your knuckles the months, it goes long, short, long, short, long, short, long, long, short, long, short, long

we have leap years every fourth year (2004, 2008, 2012 and so on)
we miss a leap year every 100 years (1700, 1800 and 1900 aren't leap years)
and we add a leap year every 400 years (1600, 2000 and 2400 are and will be leap years)
the leap year funkiness is so dates will stay within their season so you wont have Christmas in the summer in 10,000 years (looking at you Muslim calendar)

anyways all those numbers are nifty but to calculate the day of the week (will be referenced as DoW from now on) we need some tables.



now's the time to grab a pen and paper and listen closely, this table will let you calculate the DoW.
first thing you'll need is grab your date lets use today (15th of April 2020).
you write down your 100s of years (the r's you're seeing means remainder when you divide the 100s by 4) and look to what it corresponds on the # column of the table. in our case 20=0
then you look at the remaining year digits (notice how they skip a place every four years because of the leap year). In our case 20=4
then you take the month (the green months are for leap years). In our case April=6
lastly you write down the day of the month. 15
you add them all up 0+4+6+15=25
then you divide by seven and look at the remainder 25/7=3 r4
you look at the DW column and see what the remainder on the # column corresponds to and now you know the day of the week.

 

What the f-

 

My brain not big enough

 

My brain just exploded I cannot handle the sciencey mathy stuff

 

There are no remainders, only fractions.

 

As a math nerd, I love things like this. Thx

 

This really be a Wednesday moment

 

Today is in fact today.

 

now make this for minecraft days

 

Spoiler: F3

 

its really quite simple, I have summed it up for ya'll:

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i am big brain

 

you can write it all as one equation, it changes depending on how you input the date and it is pretty big

 

My math OCD is here to thank you

 

All the computer science courses I have ever taken use the calculation of a leap year problem as an exercise in Boolean logic and comparison so this is drilled into my brain

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Wouldn’t the limit at the top evaluate to infinity?