The great German mathematician Karl Fredrich Gauss devised a beautifully simple formula in 1800 to calculate the day of the week corresponding to any date.
N = D +E+F+G+(G/4)
Day of week = N mod 7.
Let us understand the formula with an example. I want to find the day for the date "15 September 1959".
Step 1. D = Day of the month - Here it is '15'
2. E = a number allotted by Friedrich for each month
Month E
Jan 1 0
Feb 2 3
Mar 3 2
Apr 4 5
May 5 0
June 6 3
July 7 5
Aug 8 1
Sep 9 4
Oct 10 6
Nov 11 2
Dec 12 4
in our case E = 4
3. Next F : Divide the century by 4 , if reminders are 0,1,2,3, Then
F = 0,5,3,1 respectively
our case : 19/4 reminder is 3, so F=1
4. G: Last two digits of the year =59
5. (G/4) tells: divide G by 4 and take only whole number of the answer. Hence 59/4=14.
Now putting everything together in the formula , N= D+E+F+G+(G/4)
6. N= 15 +4+1+59+14 =93
Day = 93 Mod 7
That is divide 93 by 7 and take the reminder it is 2
second day of week. It is Tuesday!
Got it finally
Also cross-checked using the website "Timeanddate.com".(May be, this is algorithm used in the site also). You can find out day of the next new year. Hope, it does not fall on a Sunday.
Let us appreciate the genius Karl Friedrich.
------------------------------------------