Zeller's Congruence - Examples

Examples

For January 1, 2000, the date would be treated as the 13th month of 1999, so the values would be:

q = 1
m = 13
K = 99
J = 19

So the formula evaluates as (1 + 36 + 99 + 24 + 4 − 38) mod 7 = 126 mod 7 = 0 = Saturday

(The 36 comes from (13+1)*26/10 = 364/10, truncated to an integer.)

However, for March 1, 2000, the date is treated as the 3rd month of 2000, so the values become

q = 1
m = 3
K = 0
J = 20

so the formula evaluates as (1 + 10 + 0 + 0 + 5 − 40) mod 7 = −24 mod 7 = 4 = Wednesday

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