Zeller’s Rule Formula:
,
1) K = Date. So, for 06/08/1990, we take K=06
Zellers rule, months start March.
2) M = Month no.
So,…
March = 1,
April = 2,
May = 3
so on… till
Dec = 10,
Jan = 11
Feb. = 12
So, for 06/08/1990, M=6
3) D = Last two digits of the year
So, in our example of 6/08/1990 D=90
Also remember that when you have to find day of the first or second month of any year, then Year=Given year-1
When you want to find Day of 15-2-1990.,
K=15,
Month=12,
D=Given Year-1=1990-1=1989=89 [Thanks Vineet for the Correction]
4) C = The first two digits of century
So, in our example of 06/08/1990.. C = 19.
Let us now calculate the day for 06/08/1990 with the formula above. Remember that the values of K, M, D and C are 06, 06, 90 and 19 respectively.
The formula is F = K + [(13xM – 1/5] + D + [D/4] + [C/4] – 2C
Replacing the values in the formula, we get
F = 06 + [{(13 x – 1/5] + 90 + 90/4 + 19/4 – (2 x 19)
Therefore,
F = 06 + 77/5 + 90 + 90/4 + 19/4 – 38
Which gives..
F =06 + 15.4 + 90 + 22.5 + 4.75 – 38
F =06 + 15 + 90 + 22 + 4 – 38
Therefore, F = 99
Now that you have a numerical value for the day, divide the number by 7. We need the remainder only. For example, in this case, the remainder is 1.
Now, match the remainder with the chart below:
1 = Monday
2 = Tuesday
3 = Wednesday
4 = Thursday
5 = Friday
6 = Saturday
7 = Sunday
Here, 1 represents Monday.
So by Zeller’s rule, 6th of August, 1990 was on a Monday.