Rosh Hashanah and Yom Kippur

[jnf40]

Does anyone know how I would find the dates that Rosh Hashanah and Yom Kippur
are on by using a given date? Right now I have a workbook that sets up a
timesheet for the year. Due to the layout of the timesheet I would need to
have the date of Rosh Hashanah and Yom Kippur be placed in a cell then
compare this date to the day on the timesheet to perform the formatting to
show the holiday. When the workbook starts the first sheet is always
September and then the workbook ends in August of the next year, all the user
is required to do is enter the Fiscal year. So for example the user would
enter 2008 and the workbook would contain the worksheets Sep_2007 through
August_2008. I was able to get all the other holidays I needed, but am having
trouble with these two. I am using Excel 2003. I have looked on line but all
the things I have found I can't figure out how to incorprate them into my
code, it looks like a lot of various functions are needed and most are
written for another version of VBA, I believe. Any and all help is greatly
appreciated.

 

[Ron Rosenfeld]

Does anyone know how I would find the dates that Rosh Hashanah and Yom Kippur
are on by using a given date? Right now I have a workbook that sets up a
timesheet for the year. Due to the layout of the timesheet I would need to
have the date of Rosh Hashanah and Yom Kippur be placed in a cell then
compare this date to the day on the timesheet to perform the formatting to
show the holiday. When the workbook starts the first sheet is always
September and then the workbook ends in August of the next year, all the user
is required to do is enter the Fiscal year. So for example the user would
enter 2008 and the workbook would contain the worksheets Sep_2007 through
August_2008. I was able to get all the other holidays I needed, but am having
trouble with these two. I am using Excel 2003. I have looked on line but all
the things I have found I can't figure out how to incorprate them into my
code, it looks like a lot of various functions are needed and most are
written for another version of VBA, I believe. Any and all help is greatly
appreciated.

Calculating Hebrew dates is extremely complicated. I believe the simplest
procedure for you would be a lookup table.

It would take you a lot less time to enter the dates for the next ten-twenty
years than to program to calculate these dates.
--ron

 

[joeu2004]

Calculating Hebrew dates is extremely complicated.

That would have been my guess, too. In fact, I would have thought it
was impossible, given the addition of Adar II (well, Adar I)
occassionally.

But the following URL claims to offer a formula:
http://quasar.as.utexas.edu/BillInfo/ReligiousCalendars.html .

I cannot vouch for the formula. I am suspicious of the "postponement
rules" that follow it. Since I am not aware of any postponement of
Rosh Hashanah, I suspect those rules are fixes for computational
errors in the formula.

But if it works, it does not look too difficult to implement. Be sure
to read the entire article to understand the special notation.

 

[Ron Rosenfeld]

That would have been my guess, too. In fact, I would have thought it
was impossible, given the addition of Adar II (well, Adar I)
occassionally.

But the following URL claims to offer a formula:
http://quasar.as.utexas.edu/BillInfo/ReligiousCalendars.html .

I cannot vouch for the formula. I am suspicious of the "postponement
rules" that follow it. Since I am not aware of any postponement of
Rosh Hashanah, I suspect those rules are fixes for computational
errors in the formula.

But if it works, it does not look too difficult to implement. Be sure
to read the entire article to understand the special notation.

There are, indeed, postponement rules.

Of course, there is an old joke about one Jew asking another "when is Rosh
Hashannah this year". The first Jew responded: "The same day as always. Its
on the first of Tishri".

Here are the rules from another source:

========================================
The first day of the calendary year, Rosh HaShanah, on 1 Tishri is determined
as follows:

1. The new year starts on the day of the new moon that occurs about 354 days
(or 384 days if the previous year was a leap year) after 1 Tishri of the
previous year

2. If the new moon occurs after noon on that day, delay the new year by one
day. (Because in that case the new crescent moon will not be visible until the
next day.)

3. If this would cause the new year to start on a Sunday, Wednesday, or
Friday, delay it by one day. (Because we want to avoid that Yom Kippur (10
Tishri) falls on a Friday or Sunday, and that Hoshanah Rabba (21 Tishri) falls
on a Sabbath (Saturday)).

4. If two consecutive years start 356 days apart (an illegal year length),
delay the start of the first year by two days.

5. If two consecutive years start 382 days apart (an illegal year length),
delay the start of the second year by one day.

Note: Rule 4 can only come into play if the first year was supposed to start on
a Tuesday. Therefore a two day delay is used rather than a one day delay, as
the year must not start on a Wednesday as stated in rule 3.

Of course, now we have to calculate the new moon:

A calculated new moon is used. In order to understand the calculations, one
must know that an hour is subdivided into 1080 ``parts''.

The calculations are as follows:

The new moon that started the year AM 1, occurred 5 hours and 204 parts after
sunset (i.e. just before midnight on Julian date 6 October 3761 BC).

The new moon of any particular year is calculated by extrapolating from this
time, using a synodic month of 29 days 12 hours and 793 parts.

Note that 18:00 Jerusalem time (15:39 UTC) is used instead of sunset in all
these calculations.

===================================================

Ah, yes, simple to implement.

Very quickly, here are the Gregorian dates for the next ten Rosh Hashanna's (1
Tishri)


September 29, 2008
September 18, 2009
September 8, 2010
September 28, 2011
September 17, 2012
September 05, 2013
September 25, 2014
September 14, 2015
September 21, 2017
October 03, 2016

The first day of Rosh Hashanna begins on the evening of those Gregorian dates
and goes for 24 hours. Depending on one's "sect", one would celebrate either
one or two days. Yom Kippur is on the tenth day of Tishri and also runs from
sunset to sunset.

==================================
Here is yet another source: http://www.jewfaq.org/calendar.htm

I cannot vouch for the accuracy of your source, either.
--ron