20

The epoch for the Jewish calendar is the creation of the world, not the Revelation at Sinai which traditionally occured about 2500 years later and marks the beginning of distinctly Jewish national religious obligations.


19

There is some discussion in the Jerusalem Talmud (M'gilla 7a-b) regarding which of the two Adars is considered the leap month (incidentally, halachic ramifications are discussed ad loc.). Medieval commentators interpret the Talmud as concluding that Adar I is the extra month (see Rashi to Rosh HaShana 19b, s.v. kamma ibbur hashana; see also Tosafos ibid., s....


18

Actually, Miketz does not always fall out on Chanukah. It appears that whoever told me that was mistaken. :) I ran some code (using my JavaScript Hebcal API) and discovered that in the 100 years from 5700-5800, Miketz is not on Chanukah 10 times. In 5703, 5706, 5710, 5730, 5733, 5737, 5757, 5761, 5781, and 5784, Miketz fell out on the 4th of Tevet, just ...


16

You are correct that the .NET implementation is apparently not consistent with Halacha (i.e. Jewish law) (Orach Chaim 55:10 and Mishne Berurah ibid) and your first 2 rules are correct and consistent with Halacha. Jewish law (ibid, MB 45) calculations are correctly implemented in HebCal contrary to your third rule. Specifically, if a boy is born on 30 ...


15

The discrepancy has been raised repeatedly over the centuries, by scholars Jew and non-Jew, Orthodox or not, alike. Rabbi Shimon Schwab penned an essay on it whereby he very much raised the possibility that the non-Seder-Olam chronology may be correct, though later referring to it as a "thought experiment." In his taped lectures on the history of the ...


14

Rashi in the linked Gemara says that the reason we are "marbim b'simcha" is because they are "ymei nisim k'mo Purim v'Pesach" based on which some conclude that Adar Rishon is not included, as no miracles happened in that time period. The Levush (685:1) says that we do not increase simcha in Adar 1. The Sfas Emes says we do. Some want to conclude based on ...


14

This is discussed in the Talmud (Shabbat 114) and the Rambam rules (Shabbat 5:21) that no Havdallah is recited after Shabbat when Yom Kippur falls on Sunday.


14

After some much Hebrew googling, it seems as though the rationale is the other way around. Adar was doubled because it was the last month of the calendar (which started at Nisan with Passover) back then. The decision was to celebrate Purim (and all the other events) in the second Adar as to keep both redemption celebrations close (Purim and Passover). ...


13

Your question and DoubleAA's comment on my original answer have inspired me to do some research and learn some really fascinating information about the Hebrew calendar. First, some background information: Our current 19-year intercalary cycle was instituted by Hillel II in the fourth century CE. The calendar is a lunisolar calendar which typically has 12 ...


13

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), Sabbath is different in that it always repeats every seventh day, regardless of any calendar. This is one reason given why, in the central prayer of Sabbath/...


12

The Ritva writes (Rosh Hashana 11a): ויומי ניסן לאו דוקא אלא כל מקום ומקום לפי מה שהוא דמלבלבי.‏ "The days of Nissan" is not precise, but rather every place according to when the trees bud. Based on this, Rabbis Yitzchok Yaakov Weiss (Minchat Yitzchak 10:16) and Tzvi Pesach Frank (Har Tzvi OC 118) ruled that in the Southern Hemisphere the blessing ...


12

HebCal is a full Hebrew calendar that provides lists of all the Jewish holidays, for any year. In the interest of full disclosure, i have done volunteer programming for them, but am not officially affiliated. Here is a list of all the Jewish holidays for the year 5775 (this year). Note that not every item on that list is a full holiday where work is ...


12

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 fact.” The Ger’s birthday thus remains the date that he was physically born on. Note that there is no actual halachic significance to a person’s ...


12

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 intercalating a year (e.g. damaged roads and bridges to Jerusalem, ripening of the grain and fruits). Actually, one of the reasons for introducing a calculated ...


11

They are a Gershayim, a Hebrew diacritic used in a number of ways, but generally to indicate that a certain set of letters does not spell a word in the ordinary sense. In this case, it is used to indicate that the letters are to be taken as numerals.


10

The Babylonian calendar wasn't adopted exactly as it was, but the names of the months were. This was recognized by the Sages in the Gemara, Yerushalmi Rosh Hashana 1:2. Why the Jews adopted these Babylonian names is a good question. In fact, it seems like the Jews did have their own ancient names for the months, such as 'Ziv' and 'Bul', which are ...


10

It has been used 11 times so far since the enactment of the fixed calendar in 4119. It was used in 4179, 4257, 4504, 4602, 4849, 5096, 5194, 5441, 5519, 5688, and 5766. The next time it will be used is 6013 if we still have a fixed calendar then. You can read about this exceedingly rare Dechiya and its history here.


10

In Israel, only the first night is a full holiday, and as such, the Seder is only ever on the first night. In the Diaspora, both the first and second nights are full holidays. The Seder should be done on both nights. If, for some reason, someone is really only able to do one of them, it should be the first. This is because the first night is a Biblical ...


10

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 work at all can be done) and such that Hoshana Rabba can't fall on Shabbat. Most months are of fixed length, so this effectively limits all holidays in some ...


10

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 that it took place on Yom Kippur. He says that further analysis is required to reconcile the two passages: Mateh Yehuda O.C. 584:2 קורין וה' פקד וכו' כתב הר"...


10

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 Avraham, Biur HaGra, Biur Halachah.) If we were to also prevent Yom Kippur from falling on Shabbat, that would lead to a situation where the new moon of ...


9

The best time? Get on the next flight. (listen to a clip of Gershon Veroba's song) But as for the most common/popular times to come: I am the research assistant (intern) on a study (currently unpublished) examining patterns of aliyah. (We sent the draft to the Ministry of Immigrant Absorption for feedback, and more data, but that's probably on hold for the ...


9

Per the Nitei Gavriel Pesach Volume 3 Chapter 19:9 one may prepare them on Sheviyi Shel Pesach so long they made an Eruv Tavshilin.


9

There are two main Regalim - Pesach and Sukkot. Each one has another one-day mini yom-tov without special mitzvos afterwards. They are each called an "Atzeret" since they have no special mitzvot and are a culmination of the previous holiday. 7 weeks after the beginning of Pesach is Shavuot/Atzeret, and the day after Sukkot is Shemini Atzeret. The ...


9

The gemara in Megillah 6b-7a explains why when it investigates the Mishnaic statement that in a leap year, one is required to read the megillah in the second Adar to be yotzei the requirement. (as per dafyomi.co.il) R. Eliezer says, every year we celebrate in the month next to Shevat. R. Shimon says, every year we celebrate in the month adjacent to Nisan. ...


9

To solar cycle represents continuity and consistency. The lunar cycle represents rise and fall, והחיות רצוא ושוב. The two cycles don't inherently mesh, and it takes the actions of people (as represented by Beis Din which sets the leap year) to combine the two. See here for a similar expression of this idea. In terms of lessons in Avodas Hashem, there are ...


9

Technically you could date a check in Israel with the year 5774, and it would be valid; however, few people do so. The "Hebrew date", including the year, is used on Jewish marriage and divorce documents -- though they specify "according to the year 5774 to the world's creation, according to the counting used in this location of X", to make clear that we're ...


9

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 of the Rokeah's Sefer HaShem (page 133) from the late 12th-early 13th century: ראש השנה א', חשון ב', כסליו א' It is also found in Goldschmidt's edition of ...


9

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 though the current calendar does have an error of one day in 216 years, we cannot fix that until the Mashiach comes and a new Sanhedrin appointed. As we can ...


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