There were two adjustments of the old lunar cycle: a "solar equation", decrementing the epact by 1, whenever the Gregorian calendar drops a leap day (3 times in 400 calendar years), and a "lunar equation", incrementing the epact by 1, 8 times in 2500 calendar years (seven times after an interval of 300 years, and the eighth time after an interval of 400 years).
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