Understanding your calculation
Method, example and limitations
How the calculation works
A weekday calculation maps a calendar date to its position in the seven-day week. The calendar system and local date must be identified consistently.
Example to check
January 1, 2000 was a Saturday in the Gregorian calendar and can be used as a simple reference check.
Before using the result
Historical calendar reforms and local conventions can complicate older dates. An ordinary modern Gregorian calculation does not resolve all historical-date questions.