Determination of the day of the week Correction for Leap Year gives "3". Answer, "Wednesday". Since 23 February 1676 (counting February as the second month) is, for Carroll, the same day as Gregorian 4 March 1676, he fails to arrive at the correct answer, namely "Friday," for an Old Style date that on the Gregorian calendar is the same day as 5 March 1677. Had he correctly assumed the year to begin on the 25th of March, his method would have accounted for differing year numbers - just like George Washington's birthday differs - between the two calendars. It is noteworthy that those who have republished Carroll's
Determination of the day of the week where is the day of the week (counting upwards from 1 on Sunday instead of 0 in Gauss's version); and , , and are numbers depending on the day, month, century and year which are tabulated in the "Complete table: Julian and Gregorian calendars" above. Note that the numbers tabulated for y can also be described by the following equation: Where So, for example, if you want to find 'y' for the year 1987: In Zeller’s algorithm, the months are numbered from 3 for March to 14 for February. The year is assumed to begin in March; this means, for