Talk:Mathematics of the Jewish Calendar/Gauss' Formula for the Date of Pesach

Can you give a reference to where Einstein said this?

Usefulness?
I don't know whether this is the original formula or a derviation. It doesn't seem particularly useful because you have to know both the Jewish and Gregorian (or Julian) years. That seems to presume you have a way of converting from Jewish to Gregorian/Julian year or vice versa. If you have that, then you are pretty close to not needing the information this formula provides. The date of Pesach on the Jewish calendar is always the same. It is only vis a vis the Gregorian/Julian calendar that it appears to move. So the Jewish year must not be a factor. A useful formula would not depend on knowing the Jewish year.

Can we determine the date of Pesach on the Gregorian/Julian calendar directly without knowledge of the Jewish year?

For the dates of interest (Mar/Apr), the Jewish year is 3760 + Year. The result is for the Julian calendar, which can be converted from the Julian by G = J - int(J/100) + int(J/400) - 2

Is there a link to Gauss' original paper or even better a known-good translation into English? 77.127.248.87 (discuss) 15:40, 23 April 2014 (UTC)

There is a Discussion of Gauss' paper in English, it explains all the formulae used and what they mean, and a Java program at the end that does the calculations given a year as input. There are some interesting intermediate calculations in the math of this article that is explained in the pdf document. For example:

Apocaloptimist (discuss • contribs) 08:44, 25 January 2020 (UTC)
 * The value of 'a' is 0-18. If
 * 0-6 next year will be a leap year
 * 5-11 last year was a leap year, and
 * 12-18 this year is a leap year.
 * The value of 'c' is 0-6. This translates to
 * The value of 'm' is the fraction of the day, if multiplied by 25920 the result is the number of haleqim since 6pm of the current day

Appropriateness?
"Note that in the very long term, due to calendar drift, it may be hard to know which year of the Julian calendar this Nisan 15th is in. (See Mathematics of the Jewish Calendar/The long-term accuracy of the calendar.)"

This sentence is not appropriate. Pesach is a Jewish holiday, not a civil observance and not an abstract date on the calendar. There is no "very long term" issue with respect to drift. The Jewish calendar lasts only until the year 6000 (this year is 5774). This statement quoted above is not relevant or helpful. I suggest it be removed.77.127.248.87 (discuss) 16:01, 23 April 2014 (UTC)

While I agree that Pesach is a Jewish Holiday, the Date of Pesach (which this article is about) is a date on the calendar. The work of Gauss is based on a proleptic Jewish calendar, and it makes as much sense to determine when Pesach was in 3700BC (before the exodus from Egypt) as it does to calculate MLK day in 1865 (before MLK was born). Nevertheless, the formula simply provides a date that Pesach would have been/will be observed if no changes are made to the way the calendar is calculated and the same method was used before the calendar even existed. In fact, this rule does not take into account 2 AM not being delayed (even though it starts on a Friday) although an amendment to the calculation could be made to adjust it (like if A < 2 M = M - 1) but since the formula has no input restrictions, caveats about past and future dates are appropriate.

I think a better wording would be Gauss' Forumla for the Date Of Pesach (valid from 3 AM to 9999 AM) or some such. The formula is still accurate up to 22000 AM+, but if the calendar actually ends in 6000 AM then 22000 and 9999 and certainly any mention of drift are moot. Apocaloptimist (discuss • contribs) 09:09, 25 January 2020 (UTC)