The lunations are supposed to consist of twenty-nine and thirty days alternately, or the lunar year of 354 days; and in order to make up nineteen solar years, six embolismic or intercalary months, of thirty days each, are introduced in the course of the cycle, and one of twenty-nine days is added at the end.
The Year Is Luni Solar, And, According As It Is Ordinary Or Embolismic, Consists Of Twelve Or Thirteen Lunar Months, Each Of Which Has 29 Or 30 Days.
Thus The Duration Of The Ordinary Year Is 354 Days, And That Of The Embolismic Is 384 Days.
If The Remainder Be 3, 6, 8, 14, 17 Or 19 (O), The Year Is Embolismic; If Any Other Number, It Is Ordinary.
To Compute The Times Of The New Moons Which Determine The Commencement Of Successive Years, It Must Be Observed That In Passing From An Ordinary Year The New Moon Of The Following Year Is Deduced By Subtracting The Interval That Twelve Lunations Fall Short Of The Corresponding Gregorian Year Of 365 Or 366 Days; And That, In Passing From An Embolismic Year, It Is To Be Found By Adding The Excess Of Thirteen Lunations Over The Gregorian Year.