Question: My siddur tells me to start saying the prayer for rain in the Amidah on the night preceding December 5 or 6. Why does it use a secular date rather than a Jewish one?

Answer: That's right. From now until the year 2100, in a regular year we start saying the prayer for rain on the night of December 4, and in the year before a (civil) leap year (2023, 2027, 2031, 2035, 2039), on the night of December 5. How did this come to be? Let's start at the beginning. As a rule of thumb, Jewish holidays and customs always follow the Jewish calendar, which is linked to the phases of the moon. One exception to this rule is the special prayer requesting rain, which Jews in the Diaspora begin saying on the night preceding December 5 (or 6). To understand why, let’s take a look at the history and significance of this small but important prayer. In this article: Praying for Rain

In Israel

In the Diaspora

Now Some Math

Calendar Issues

What to Do?

Praying for Rain Jews have been praying for rain for millennia. In the ancient land of Israel, rain was a life-and-death concern. A good rainy season meant a good harvest and ample drinking water, while a drought could be fatal to livestock and cripple the economy. So when the Men of the Great Assembly set out to codify the prayers, they made sure to add a prayer for rain to the daily Amidah (silent prayer). In fact, rain appears twice in the Amidah. It is first mentioned in the second blessing, as one of a string of natural and supernatural wonders that G‑d performs. Not least among them is that “He causes the wind to blow and the rain to fall.” Here we are praising G‑d, who brings rain, but we are not actually asking for rain. It is only later, in the blessing requesting a bountiful year, that we ask G‑d to “bestow dew and rain for blessing upon the face of the earth . . .” In both instances, the rain-related phrase is said only during the winter (Israel’s rainy season). However, the two prayers follow slightly different schedules. We begin to say “He causes the wind to blow and the rain to fall” on Shemini Atzeret. But, as you point out, we start saying the second prayer, the actual request for rain, only at the beginning of December. Why the differing start dates? It’s an interesting story . . .

In Israel The Jews of ancient Israel made three pilgrimages to Jerusalem each year, for the holidays of Passover, Shavuot and Sukkot. Now, the official rainy season begins on Shemini Atzeret, when the Jews were about to start their journey back home after the festival of Sukkot. As much as they wanted the rain, they chose to delay their supplications in the interests of a safer and easier trip. That is how the practice of delaying the prayer for rain began. In Israel, the prayer was begun only 15 days after Shemini Atzeret (the 7th of Cheshvan), allowing enough time for even the Jews living near the Euphrates to return home. This custom is followed by Jews living in Israel until today. Outside of Israel, however, a more complicated calculation became necessary.

In the Diaspora For much of our history, the primary Jewish community in the Diaspora was in Babylonia (modern-day Iraq), where the terrain is on a lower altitude than Israel’s, and they do not need rain until much later. Therefore, the sages instituted that Jews living in the Diaspora should start praying for rain only 60 days after the start of the halachic autumn, which is known as tekufat Tishrei. (This should not be confused with the autumn equinox, which is usually September 22 or 23.) I will explain soon when exactly that is. Nowadays very few Jews live in Babylonia, and the Jews of North America need rain at a different time than the Jews of Singapore. Nevertheless, we all start asking for rain on the day established for the Jews in Babylonia, regardless of when rains are actually needed in our respective locales. The Rebbe, Rabbi Menachem M. Schneerson, Of Blessed Memory, explains that even Jews living in the Southern Hemisphere, where the seasons are reversed, should follow the schedule established for the Jews of Babylonia, because we pray for the needs of the Jewish people as a whole, most of whom reside in the Northern Hemisphere. Obviously, this does not preclude us from praying for rain at other times. An individual or community that needs rain at a different time may add a personal prayer into the sixteenth blessing of the Amidah, “Shomei’a Tefillah,” where we add our unique requests.

Now Some Math We now know that the custom of Jews in the Diaspora is to start praying for rain 60 days after the onset of tekufat Tishrei. But when exactly is that? In the third century, the Talmudic sage Shmuel calculated the length of the solar year as 365 days and 6 hours. Since the year is subdivided into four seasons, or tekufot in Hebrew, it follows that each tekufah is 91 days and 7½ hours (365.25 ÷ 4 = 91.3125). This calculation happens to correspond with the Julian calendar, which was widely used from the year 45 BCE until the introduction of the Gregorian calendar in 1582 CE. Based on this, tekufat Tishrei always began on September 24 on the Julian calendar, and 60 days into tekufat Tishrei was November 22.

Calendar Issues It eventually became clear that the solar year is actually 11 minutes and 14 seconds shorter than previously calculated, and that the calendar was slowly but surely drifting ahead. In the year 1582, the spring (vernal) equinox—which had been on March 25 at the introduction of the Julian calendar—actually occurred on March 11. This was about 10 days earlier than March 21, which is the day that had been “fixed” as the vernal equinox in the year 325. To remedy this, Gregory XIII made two changes: He shifted the calendar back by removing 10 days in October, making October 5 of the year 1582 into October 15. This restored the spring equinox to March 21. To ensure that the calendar would not shift again, Gregory implemented that every 128 years (or, more roughly, three times every 400 years), one day would be removed from the calendar. (This is because the discrepancy of 11 minutes and 14 seconds accumulates into a whole extra day every 128 years.) The extra day normally appended to the month of February every four years (causing a leap year) would not be added to all centaury years, except for those years which are multiples of 400. (Thus, it was not added in the years 1700, 1800 and 1900. However, it was added to the years 1600 and 2000.) If you’re still following me, it should be clear that the old calendars (Jewish and Julian) drift away from the new (Gregorian) calendar at a rate of three days every 400 years. It’s important to note that the Jewish sages were well aware that this calculation was not completely accurate. In fact, for most purposes the Jewish calendar follows the more accurate calculations of Rabbi Adda bar Ahavah, who gives the length of the solar year as 365 days, 5 hours, 55 minutes and 25.4 seconds. However, the sages of the Talmud chose to calculate the length of a solar year as 365.25 days for the prayer for rain and for Birchat Hachamah (the blessing of the sun), because it made the calculations much simpler for the average person to perform.