Posted by & filed under Observance.

Calendrical Calculations Hebcal uses the algorithm defined in Calendrical Calculations by Edward M. Reingold and Nachum Dershowitz.

Birthday

Reingold and Dershowitz write:

The birthday of someone born in Adar of an ordinary year or Adar II of a leap year is also always in the last month of the year, be that Adar or Adar II. The birthday in an ordinary year of someone born during the first 29 days of Adar I in a leap year is on the corresponding day of Adar; in a leap year, the birthday occurs in Adar I, as expected. Someone born on the thirtieth day of Marcheshvan, Kislev, or Adar I has his birthday postponed until the first of the following month in years where that day does not occur. [Calendrical Calculations p. 111]

Yahrzeit

The rule for a Yahrzeit is a little different:

The customary anniversary date of a death is more complicated and depends also on the character of the year in which the first anniversary occurs. There are several cases:

  • If the date of death is Marcheshvan 30, the anniversary in general depends on the first anniversary; if that first anniversary was not Marcheshvan 30, use the day before Kislev 1.
  • If the date of death is Kislev 30, the anniverary in general again depends on the first anniverary — if that was not Kislev 30, use the day before Tevet 1.
  • If the date of death is Adar II, the anniversary is the same day in the last month of the Hebrew year (Adar or Adar II).
  • If the date of death is Adar I 30, the anniversary in a Hebrew year that is not a leap year (in which Adar only has 29 days) is the last day in Shevat.
  • In all other cases, use the normal (that is, same month number) anniverary of the date of death.

[Calendrical Calculations p. 113]

Yahrzeit Example

For example, suppose Ploni ben Ploni passed away on 14 March 2001. That date corresponds to the 19th of Adar, 5761. Since 5761 was not a leap year, there was only one Adar that year (i.e. the date of death occurred in 12th month of the Hebrew year).

Suppose one wishes to observe the yahrzeit in Hebrew year 5765. Since 5765 is a leap year and none of the other rules applies, we use the same month number as the date of death. In a leap year the 12th month is Adar I, so the yahrzeit is observed on 19th of Adar I, 5765 (28 February 2005).

Variations

On page 114, Reingold and Dershowitz write:

There are minor variations in custom regarding the anniversary date in some of these cases. For example, Spanish and Portuguese Jews never observe the anniversary of a common-year date in Adar I.

There are undoubtedly many differing opinions regarding when to observe an Adar yahrzeit.

Here are two articles which offer differing opinions from our implementation:

For all matters of halacha, consult your local rabbi.

9 Feb 2005: added errata at Nachum Dershowitz’s request.
9 Mar 2005: Added Ploni ben Ploni example.
9 Mar 2014: Added links to opinions by Rabbis Golinkin and Schachter

Posted by & filed under Torah Readings and Sedra Schemes.

Jews living in the Diaspora (outside of modern Israel) typically observe two days of chag on holidays that are Yom Tov (holidays where work is forbidden, called yontiff in Yiddish). In Israel, only one day of chag is observed.

Sometimes, depending on the calendar, the Diaspora observes the second day of chag on Shabbat, and the holiday Torah reading pushes the regular weekly Torah reading back a week. Since Israel has only one day of chag, they read the regular weekly Torah reading. Thus, the Parashat ha-Shavuah ends up being different.

When using the “Weekly sedrot on Saturdays” option on the custom calendar, select the appropriate option depending on where you live (Israeli sedra scheme for those living inside Israel, Diaspora for everyone else).

Posted by & filed under Torah Readings and Sedra Schemes.

“Many congregations pattern their weekly Torah reading cycle after a system similar to the one used in ancient Israel during the rabbinic period. In this system, the traditional parashiot are each divided into three shorter segments, and the whole Torah is completed once every three years. The system has both advantages and disadvantages, but its ability to shorten the length of Torah reading without sacrificing the complete reading of the Torah on a regular basis has made it the choice of some synagogues in the Conservative Movement.”

A Complete Triennial System for Reading the Torah, Committee on Jewish Law and Standards of the Rabbinical Assembly

Posted by & filed under Torah Readings and Sedra Schemes.

Leyning coordinators can download these Comma Separated Value (CSV) files and import into Microsoft Excel or some other spreadsheet program. These spreadsheets contain the Torah readings for the current year and 5+ years into the future.

Download Full Kriyah and Triennial spreadsheets

Note that in September 2013, we replaced the large multi-year fullkriyah.csv file with separate files for each Hebrew year.

Posted by & filed under Observance.

All Jewish Holidays begin the evening before the date specified. This is because the Jewish day actually begins at sundown on the previous night. Sometimes, for clarity, the Erev Holiday is also included.

Posted by & filed under Observance.

CH”M is an abbreviation for Chol Ha-Mo’ed. Chol Ha-Mo’ed are the intermediate days of Passover and Sukkot, when work is permitted.

Posted by & filed under Observance.

For example, Tzom Tammuz is always on the 17th of Tammuz, but in the year 5772 (2012 C.E.) it is on the 18th of Tammuz. The answer has to do with Shabbat:

“The Hebrew year contains several fast days that, though specified by particular Hebrew calendar dates, are shifted when those days occur on Saturday. The fast days are Tzom Gedaliah (Tishri 3), Tzom Tevet (Tevet 10), and Tishah be-Av (Av 9). When Purim is on Sunday, Ta’anit Esther occurs on the preceding Thursday… Each of the other fast days, as well as Shushan Purim (the day after Purim, celebrated in Jerusalem), is postponed to the following day (Sunday) when it occurs on Saturday.”

Reference: Calendrical Calculations, Edward M. Reingold, Nachum Dershowitz, Cambridge University Press, 2001, page 109.

Posted by & filed under Developers, APIs, RSS Feeds, Source Code.

Hebcal.com’s Add Shabbat Times to your Website tool lets you create custom HTML tags to which display weekly candle-lighting times directly on your web page. The result looks something like this:

Shabbat times for Chicago, IL

Candle lighting: 4:08pm on Friday, 02 January 2004
This week’s Torah portion is Parashat Vayigash
Havdalah (72 min): 5:39pm on Saturday, 03 January 2004

1-Click Shabbat Copyright © 2004 Michael J. Radwin. All rights reserved.

Posted by & filed under General.

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