The verse states: “They cast pur, that is, the lot” (Esther 3:7). A Sage taught the following baraita: Once the lot fell on the month of Adar, he, Haman, greatly rejoiced, for he saw this as a favorable omen for the execution of his plans. He said: The lot has fallen for me in the month that Moses died, which is consequently a time of calamity for the Jewish people. But he did not know that not only did Moses die on the seventh of Adar, but he was also born on the seventh of Adar, and therefore it is also a time of rejoicing for the Jewish people.
תניא אידך בשבעה באדר מת משה ובשבעה באדר נולד מנין שבשבעה באדר מת שנאמר (דברים לד, ה) וימת שם משה עבד יקוק וכתיב (דברים לד, ח) ויבכו בני ישראל את משה בערבות מואב שלשים יום וכתיב (יהושע א, א) ויהי אחרי מות משה עבד יקוק וכתיב (יהושע א, ב) משה עבדי מת ועתה קום עבור וכתיב (יהושע א, יא) עברו בקרב המחנה וצוו את העם לאמר הכינו לכם צידה כי בעוד שלשת ימים תעברו את הירדן וכתיב (יהושע ד, יט) והעם עלו מן הירדן בעשור לחדש הראשון צא מהן שלשים ושלשה ימים למפרע הא למדת שבשבעה באדר מת משה ומנין שבשבעה באדר נולד משה שנאמר (דברים לא, ב) ויאמר אליהם בן מאה ועשרים שנה אנכי היום לא אוכל עוד לצאת ולבא שאין ת"ל היום מה ת"ל היום מלמד שהקב"ה יושב וממלא שנותיהם של צדיקים מיום ליום ומחדש לחדש שנאמר (שמות כג, כו) את מספר ימיך אמלא
...Another [Baraitha] taught: On the seventh of Adar Moses died, and on the seventh of Adar he was born. How do we know that he died on the seventh of Adar? For it is written: So Moses the servant of the Lord died there; And the children of Israel wept for Moses in the plains of Moab thirty days; Moses thy servant is dead; now therefore arise, go over [this Jordan]; Pass through the midst of the camp, and command the people, saying: Prepare you victuals; for within three days ye are to pass over this Jordan;and [v] and the people came up out of Jordan on the tenth day of the first month; deduct the preceding thirty three days, thus you learn that Moses died on the seventh of Adar. And how do we know that he was born on the seventh of Adar? — For it is said: And he [Moses] said unto them, I am an hundred and twenty years old this day; I can no more go out and come in. Now, ‘this day’ need not be stated; why then is it stated? It teaches that the Holy One, blessed be He, sits and completes the years of the righteous [exactly] from day to day and month to month, as it is said,the number of thy days I will fulfil.
R. Eliezer, who holds that Purim is observed in Adar I makes sense for there is a principle that one should never pass up an opportunity to perform a mitzvah. But why would R. Shimon b. Gamaliel hold that Purim is delayed until Adar II.
R. Tabi says that R. Shimon b. Gamaliel wanted the redemption of Purim to be close to the redemption of Pesah. Therefore, they should be observed in adjacent months.
(ד) קָרְאוּ אֶת הַמְּגִלָּה בַּאֲדָר הָרִאשׁוֹן וְנִתְעַבְּרָה הַשָּׁנָה, קוֹרִין אוֹתָהּ בַּאֲדָר הַשֵּׁנִי, אֵין בֵּין אֲדָר הָרִאשׁוֹן לַאֲדָר הַשֵּׁנִי אֶלָּא קְרִיאַת הַמְּגִלָּה וּמַתָּנוֹת לָאֶבְיוֹנִים:
(4) If the Megillah was read in first of Adar, and the year was [subsequently] intercalated, we read it in second of Adar. There is no difference between the first Adar and the second Adar except the reading of the Megillah and alms to the poor.
(תרפט) בשנה מעוברת, יום י''ד וט''ו שבאדר ראשון, אף על פי שאין קוראים בהם המגילה, מכל מקום אסורים בהספד ותענית, ואין נופלים על פניהם, ואין אומרים בהם בתפלה מזמור יענך ה' ביום צרה, ומזמור תפלה לדוד. ונכון לנהוג בהם מקצת משתה ושמחה, י''ד לבני פרזים, וט''ו לבני ירושלים. ומה שאין קוראים המגילה באדר ראשון, לפי שנאמר (מגילת אסתר ט כא), לקיים עליהם להיות עושים את יום י''ד וט''ו''בכל שנה ושנה'', מה בכל שנה אדר הסמוך לניסן, אף בשנה מעוברת אין הפורים נוהג אלא באדר הסמוך לניסן, ולסמוך גאולה לגאולה, דהיינו לסמוך פורים לפסח, עדיף.
During a leap year, the 14th and 15th days of Adar Rishon, even though we don’t read the Megilla on them, nevertheless it is forbidden to give a eulogy or fast, and we don’t say Tachanun, and we don’t say Lamnatzeach. It is good to behave a little happier than usual and feast a little, on the 14th for the villages (outside of the walled cities), and on the 15th for the walled cities. And we don’t read the Megilla during Adar Rishon, like it says in מגילת אסתר ט כא, that is referring to the Adar that is next to Nissan, but during a leap year, we don’t celebrate Purim other than during the Adar that is next to Nissan. This is because we want to put redemption with redemption, that is Purim and Pesach, it is good.
החדש הזה — He showed him the moon in the first stage of its renewal, and He said to him, “The time when the moon renews itself thus, shall be unto you the beginning of the month”. (The translation therefore is: “This stage of renewal (חדש) shall be the moment of beginning the months”; cf. Mekhilta d'Rabbi Yishmael 12:2:2). But no Scriptural verse can lose its literal meaning, and He really spoke this in reference to the month Nisan: this month shall be the beginning in the order of counting the months, so that Iyar shall be called the second, Sivan the third.
The Beginning of the Jewish Calendar By Bernard Dickman, Ḥakira, the Flatbush Journal of Jewish Law and Thought, Vol. 8
The Jewish calendar is a lunisolar calendar consisting of 12 months annually of 29 or 30 days. An extra leap month of 30 days is added every 2 or 3 years (7 leap months in 19 years) for a total of 235 lunar months in 19 years. This 19-year cycle is called the Metonic cycle and results in the 19 Jewish years approximating 19 solar years. In this way, the Jewish holidays are always in the same season and vary by less than a month in the solar calendar.
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7 in 19
A key component of the Jewish calendar is the molad, or average conjunction, of each new month. The timing of the molad of Tishrei determines when Rosh Hashanah occurs. The molad is calculated by taking the molad of the Tishrei at creation... and adding the average time between months (29 days, 12 hours, 44 minutes and 3.33 seconds) for every month until we get to the desired month. This requires one to know how many years and months have passed since creation. The number of years we know based on our Jewish calendar. However, we do not know which years had a leap month. A basic assumption of the Jewish calendar is that it has averaged 7 leap months every 19 years. While there may have been 19-year periods with six or eight leap months, over the entire time span since creation, the Jewish calendar assumes that there have been exactly 7 leap months for every 19 years.
The Beginning of the Jewish Calendar By Bernard Dickman, Ḥakira, the Flatbush Journal of Jewish Law and Thought, Vol. 8
Historically, Sanhedrin decided when a month started and when a leap year should be added. Sometime after the destruction of the second Temple a fixed calendar was put in place... R. Avraham bar Chiyya in Sefer ha-Ibbur (1123) says that in 992 R. Hai Gaon claimed that the calendar was created in Eretz Yisrael under the leadership of Hillel II in 358/9. We do not have a copy of the cited R. Hai Gaon’s work. The earliest confirmed existence of our calendar dates to the 12th century... Many calendar historians question this dating and some say that the fixed calendar was not finalized until the 800s. A noted expert, Engineer Yaaqov Loewinger, reviews this controversy and argues that astronomical data are consistent with a 358/9 dating of the calendar.
Month Lengths
| Month | Length |
|---|---|
| Tishrei | 30 |
| Cheshvan | 29 or 30 |
| Kislev | 29 or 30 |
| Tevet | 29 |
| Shevat | 30 |
| Adar | 29 |
| (Adar I) | 30 |
| (Adar II) | 29 |
| Nisan | 30 |
| Iyar | 29 |
| Sivan | 30 |
| Tamuz | 29 |
| Av | 30 |
| Elul | 29 |
The Hebrew year can be one of six different lengths, depending on whether or not its a leap year and the length of Cheshvan and Kislev.
| Months | Cheshvan | Kislev | Type | Year Len. |
|---|---|---|---|---|
| 12 (Regular) | 29 | 29 | Chaser | 353 |
| 12 (Regular) | 29 | 30 | Kesidran | 354 |
| 12 (Regular) | 30 | 30 | Malei | 355 |
| 13 (Leap) | 29 | 29 | Chaser | 383 |
| 13 (Leap) | 29 | 30 | Kesidran | 384 |
| 13 (Leap) | 30 | 30 | Malei | 385 |