Conversion Center

Hipparchus proposed to make a 1 day correction after 4 Calippic cycles. A Hipparchic cycle lasts 111035 days instead of 111036 days (4 Calippic cycles). He decided to make that correction, because he found that the tropical year is about 1/300 of a day shorter than 365 + 1/4 days that Calippus used. This is a very decent approximation for an integer number of lunations to an integer number of days (error only 0.014 days).