Determination of the day of the week for the following month. The item for January is "0"; for February or March, "3"; for December, "12". Day-item: The total, thus reached, must be corrected, by deducting "1" (first adding 7, if the total be "0"), if the date be January or February in a leap year, remembering that every year, divisible by 4, is a Leap Year, excepting only the century-years, in `New Style', when the number of centuries is not so divisible (e.g. 1800). The final result gives the day of the week, "0" meaning Sunday, "1" Monday, and so on. Examples: 17, divided by 4, leaves
Determination of the day of the week method have failed to point out his error, most notably Martin Gardner. In 1752, the British Empire abandoned its use of the Old Style Julian calendar upon adopting the Gregorian calendar, which has become today's standard in most countries of the world. For more background, see Old Style and New Style dates. In the C language expressions below, y, m and d are, respectively, integer variables representing the year (e.g., 1988), month (1-12) and day of the month (1-31). In 1990, Michael Keith and Tom Craver published the foregoing expression that seeks to minimise the number of keystrokes needed to