In the article Calendar (q.v.), that part of chronology is treated which relates to the measurement of time, and the principal methods are explained that have been employed, or are still in use, for adjusting the lunar months of the solar year, as well as the intercalations necessary for regulating the civil year according to the celestial motions.
This Mistake Having Been Discovered, Augustus Ordered That All The Years From The Thirtyseventh Of The Era To The Forty Eighth Inclusive Should Be Common Years, By Which Means The Intercalations Were Reduced To The Proper Number Of Twelve In Forty Eight Years.
Directed Ten Days To Be Suppressed In The Calendar; And As The Error Of The Julian Intercalation Was Now Found To Amount To Three Days In 400 Years, He Ordered The Intercalations To Be Omitted On All The Centenary Years Excepting Those Which Are Multiples Of 400.
46 Sec. Now The Gregorian Rule Gives 97 Intercalations In 400 Years; 400 Years Therefore Contain 365 X400 97, That Is, 146,097 Days; And Consequently One Year Contains 365.2425 Days, Or 365 Days 5 Hours 49 Min.
The Third 3 3, Gives Eight Intercalations In Thirty Three Years Or, Seven Successive Intercalations At The End Of Four Years Respectively, And The Eighth At The End Of Five Years.