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14 votes
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When is a convert's Hebrew birthday?

Dinonline answers, Although a Ger is considered to be “born anew” when becoming Jewish, this is a halachic concept that relates to family relationship and the like, and it is not a “biological ...
NJM's user avatar
  • 14.3k
13 votes

Changing the day of Shabbos?

While the Jewish holidays are controlled by the Sanhedrin (though, notably, they are not controlled by non-Jewish governments, and even the Sanhedrin's control is bound by divinely received rules), ...
Loewian's user avatar
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12 votes
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Declare a leap year due to coronavirus?

There are two problems, both are discussed (among others) in Sanhedrin 11a. The first is that you need a Sanhedrin with a Nasi to intercalate a year. The second is that there are certain reasons for ...
Kazi bácsi's user avatar
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12 votes
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What is the א"ת ב"ש ג"ר calendar mnemonic?

The Shulchan Aruch 428:3 explains the mnemonic: סימן לקביעת המועדים א"ת ב"ש ג"ר ד"ק ה"ץ ו"ף פירוש ביום א' של פסח יהיה לעולם ת"ב וסימן על מצות ומרורים יאכלוהו ביום ...
robev's user avatar
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11 votes
Accepted

Why some biblical holidays don't occur on certain days of the week?

The current fixed calendar is arranged (by adding or taking out an extra day in Marcheshvan or Kislev) such that Yom Kippur can't fall on Friday or Sunday (so there won't be two days in a row where no ...
Double AA's user avatar
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11 votes
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Why do Kisidran years only occur when starting on a Tuesday or non-leap Thursday?

Modular arithmetic time: 385 mod 7 = 0 384 mod 7 = 6 383 mod 7 = 5 355 mod 7 = 5 354 mod 7 = 4 353 mod 7 = 3 That's how far Rosh Hashana moves from year to year. The Kisidran options are 4 and 6. ...
Double AA's user avatar
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11 votes
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Date of the Akeida?

R. Yehuda Ayash points out that there are contradictory passages in the Zohar. In Parshat Vayikra it says that the Binding of Isaac took place on Rosh Hashanah, while in Parshat Vayeitzei it implies ...
Alex's user avatar
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11 votes

Making my own Jewish calendar with paper and pencil

There's no need for a mashgiach since anyone can check on their own. Here's all you need to know to calculate any date. In years whose value is 0,3,6,8,11,14,17 modulo 19 an extra month is added after ...
Double AA's user avatar
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10 votes
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Where do we first see Cheshvan (as opposed to Marcheshvan)?

Midrash Abba Gurion to Ester (ed. Buber 3:7), which was redacted in the tenth century, refers to it as חשוון (Heshvan): לתשרי זכות הרגלים, לחשוון זכות שרה It is also found in Eisenbach's edition ...
mevaqesh's user avatar
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10 votes

Why was the calendar not arranged so that Yom Kippur never falls on Shabbat?

The fixed calendar already prevents Yom Kippur from falling on a Friday or Sunday, to avoid two consecutive days where all melachot are forbidden. (See Shulchan Aruch Orach Chaim 428:1 with e.g. Magen ...
Joel K's user avatar
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10 votes

Declare a leap year due to coronavirus?

The rabbis currently do not have the authority to declare a leap year because there is no Sanhedrin. The current calendar was set up by Hillel II and is completely fixed by calculation. Indeed, even ...
sabbahillel's user avatar
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9 votes

What did people say in Shemoneh Esrei and Kiddush of Shavuos when it didn't fall out on the 6th of Sivan?

Two basic answers exist to this question: In reality, when the calendar was decided by testimony of the new moon, this phrase probably did not exist in the prayers. Maseches Sofrim 19:4 writes: ...
הנער הזה's user avatar
8 votes
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What is the greatest number of holiday days falling on weekdays in a year?

Between Purim and the next Shemini Atzeret the calendar is completely fixed (no leap years, leap days, etc.). The four possibilities are: Purim (F), Pesach (S-Sh), Shavuot (M), Tisha b'Av (S), Rosh ...
Double AA's user avatar
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8 votes
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Why are some dates off by one day?

I think I may have discovered the answer. After mulling over the problem for a bit, I realized that not all cycles are created equally. The 19-year cycle just determines which years are leap years; it'...
DonielF's user avatar
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8 votes
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Purim and Pesach in the same month

In 1999, the day of Purim fell out on the 2nd of March. This means that first few hours of pesach fell out on the 31st of March. Same happened in 1980, 1961.... The last time that Purim fell out on ...
aBochur's user avatar
  • 3,859
8 votes
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What is the source for Hillel’s having included an expiration date in the calendar?

You write that: It’s often said that when Hillel instituted the current calendar, he set an “expiration date” of 6000 AM; at that point the calendar would be invalid. Since Mashiach presumably will ...
Joel K's user avatar
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8 votes
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Tisha b Av calendar confusion

This year the ninth day of the month of Av fell on Shabbat. Since fasting on Shabbat is forbidden, the holiday of Tisha b'av (which literally translates as "the Ninth of Av", hence the confusion) was ...
יהושע ק's user avatar
8 votes

Why does the date for the prayer for rain change from one century to the next?

The rules try to keep the date for requesting rain in the late fall. They are not perfect. No rule would be except adding the ever-changing long decimal tropical year length. If we were to take a ...
Double AA's user avatar
  • 99.5k
8 votes

What did people say in Shemoneh Esrei and Kiddush of Shavuos when it didn't fall out on the 6th of Sivan?

Rav Yehoshua ibn Shu’ib, Rabbi Mordecai ben Abraham Benet, and the Mateh Moshe (Laws of Shavuot 690) explain that for this reason the more general word 'time' is used instead of the more precise 'day' ...
Jay's user avatar
  • 6,507
8 votes
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Historical Daf Yomi calendar

I have found that Daf Yomi Calendar has the calendar for cycles 11 - 15. This site does not have any earlier cycles. I have found D.A.F.'s Talmud Tools which allows you to search back by Daf, Hebrew ...
sabbahillel's user avatar
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7 votes
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Why is there never a break between parshiot Parah and Hachodesh?

The Aruch Hashulchan in OC 685 says that there are no breaks between them because they are related to each other (unlike the others, which are unrelated to the ones next to them, meaning that Zachor ...
רבות מחשבות's user avatar
7 votes
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Which event is more infrequent?

tl;dr Over a span of 689,472 years (the complete Hebrew calendar cycle), a three-Torah shabbat happens 465,929 times, and a two-Torah weekday happens 1,009,765 times. For technical details, see below ...
Joel K's user avatar
  • 43.7k
7 votes

Sources for Rav Saddia Goan on set days for Pesach

This opinion of R. Sa'adia Ga'on is quoted by R. Avraham b. Hiyya HaNasi. In his Sefer Ha-Ibbur, he writes (ma'amar sheni, sha'ar shemini): ואמר הגאון ר' סעדיה בר' יוסף ראש הישיבה זצ"ל: קבוע היה ...
Joel K's user avatar
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7 votes
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Is the TorahCalc Molad Calculator accurate?

In short It's their algorithm. It appears that they are using an inaccurate constant of 3.3 to back into the number of chalakim from the number of seconds. This constant should instead be 3 + (1/3). ...
yydl's user avatar
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6 votes
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Why do we start saying "Veten tal umatar" during Ma'ariv?

Actually, the sixtieth day after tekufat tishrei is currently December 5th or 6th - it hasn't been December 4th for about a hundred years. We say it on maariv of the day before, because that's when it ...
Shimon bM's user avatar
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6 votes

Mean Hebrew Year Length

The Jewish year varies in length, with an extra month some years and with some years having one more or one less day than usual. Ultimately, the main reason for the variation is to keep it from ...
Isaac Moses's user avatar
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6 votes
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Mean Hebrew Year Length

A mean Hebrew month is 29 days + 12 hours + 793/1080 of an hour. Back then they would add a 13th month into the year whenever the drift appeared to be getting too big, but not on a regular schedule, ...
Double AA's user avatar
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6 votes
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Is there a pattern to whether a year is full/regular/deficient? Is there an online source that lists them?

To quote from Remy Landau's website: The 19 year cycle does not cause the Hebrew calendar to repeat itself every 19 Hebrew years. The 19 year cycle only refers to the positions of the 13-month ...
Joel K's user avatar
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6 votes
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Personality traits of being born on certain weekdays

Gemorah Shabbos 156a [I copied Sefaria's version see complete Gemorah here] כתיב אפינקסיה דרבי יהושע בן לוי האי מאן דבחד בשבא יהי גבר ולא חדא ביה After citing relevant halakhot written in the ...
פרי זהב's user avatar
6 votes

Historical Daf Yomi calendar

The Simple Luach app lists the day's daf in its calendar. Navigate to the calendar tab, and click the icon at the top right. This goes back to September 11, 1923 which lists Berachos 2 as the day's ...
Alex's user avatar
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