epact
Sign in to savethumb|Face on the Zimmer tower in [[Lier, Belgium: On the outer ring, the hand points to the golden number, or the number of the current year in the metonic cycle. The inner ring shows the epact, which is the age of the moon on the first of January of the current year.]]
Article
8 sectionsContents
- Lunar calendar
- Solar and lunar years
- 19-year cycle
- Lilian (Gregorian) epacts
- History
- See also
- References
- External links
thumb|Face on the Zimmer tower in [[Lier, Belgium: On the outer ring, the hand points to the golden number, or the number of the current year in the metonic cycle. The inner ring shows the epact, which is the age of the moon on the first of January of the current year.]]
The epact (, from () = added days) used to be described by medieval computists as the age of a phase of the Moon in days on 22 March; in the newer Gregorian calendar, however, the epact is reckoned as the age of the ecclesiastical moon on 1 January. Its principal use is in determining the date of Easter by computistical methods. It varies (usually by 11 days) from year to year, because of the difference between the solar year of 365366 days and the lunar year of 354355 days.