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.
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.
Thus The Duration Of The Ordinary Year Is 354 Days, And That Of The Embolismic Is 384 Days.
If, For A Year Immediately Following An Embolismic Year, The Computed New Moon Is On Monday, As Late As 15 Hours 30 Min.
The Intercalary Month, Veadar, Is Introduced In Embolismic Years In Order That Passover, The 15Th Day Of Nisan, May Be Kept At Its Proper Season, Which Is The Full Moon Of The Vernal Equinox, Or That Which Takes Place After The Sun Has Entered The Sign Aries.
An Ordinary Year May Comprise 353, 354 Or 355 Days; And An Embolismic Year 383, 384 Or 385 Days.