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In ancient Rome, Lustrum, was originally a sacrifice for expiation and purification offered by one of the censors of Rome in the name of the Roman people at the close of the taking of the census, which took place every five years. The Latin word lustrum has survived, and been adopted in some modern languages, in the derived sense of a period of five years.

Callippic cycle, in astronomy and calendar studies, is a particular approximate common multiple of the the tropical year and the synodic month. It was proposed by Callippus in 330 BC. Callippic cycle is a period of 76 years, as an improvement on the 19-year Metonic cycle.
A Metonic cycle was invented by Meton and lasts 6940 days. This means that a solar year is 365 d 6 h 18 min 56 s, but Callippus knew that year length was more closely to 365 + 1/4 days. So he multiplied the 19-year cycle by 4 to reach an integer number of days and dropped 1 day from the last 19-year cycle. Thus he constructed a cycle of 76 years that contains 940 lunations or 27,759 days.