Category Archives: Observance

Converting between Hebrew and Gregorian dates for very early years is mathematically possible (and is supported by our Hebrew Date Converter), but the results should be treated as approximations rather than historically precise dates.

The Hebrew calendar evolved into a fixed, calculation-based system beginning in the 4th century CE, traditionally associated with reforms attributed to Hillel II (a fifth generation amora). This shift replaced earlier dependence on eyewitness moon sightings and centralized rulings on leap years with a predictable mathematical framework. The detailed rules were recorded in writing over the following centuries and were later systematized by Maimonides in the 12th century, by which point the calendar had become uniform across Jewish communities by the medieval era.^[1]

Before the calendar rules were fully standardized in the early medieval period, both the Hebrew and civil calendars were influenced by local practice, observational methods, and later retroactive calculations. As a result, modern algorithms can project dates backward consistently, but they may not reflect how dates were actually observed or recorded at the time.

Any results for year 1752 CE and earlier published on Hebcal.com will be inaccurate. Hebcal does not take into account a correction of ten days that was introduced by Pope Gregory XIII known as the Gregorian Reformation.

Encyclopædia Britannica has an excellent introduction to the Jewish calendar. Another well written treatment of the Jewish calendar can be found in Understanding the Jewish Calendar by Rabbi Nathan Bushwick.

There are four “New Years” mentioned in the Mishnah (Tractate Rosh Hashanah 1:1), each signifying a new beginning for different aspects of life: 1 Tishrei (Rosh Hashanah), 1 Nisan (for kings and festivals), 1 Elul (for tithes), and Tu Bishvat (for trees).

Here’s a breakdown:

1st of Tishrei – Rosh Hashana – New Year for Years

This is the most widely known Jewish New Year, marking the beginning of the Jewish calendar year and the start of the High Holy Days. On Rosh Hashanah, the calendar year changes (for example, from 5785 to 5786). It’s the beginning of the agricultural, financial, and legal year (like Sabbatical years and Jubilee years).

The Torah never refers to the first day of the seventh month as Rosh ha-Shanah. That term first appears in Ezek. 40:1. In the Torah, it is called a “day of remembrance” or “a day of sounding the shofar.” Readers may be surprised to learn that Rosh ha-Shanah begins the seventh month of the Hebrew calendar rather than the first. It commemorates the creation of the world, which traditionally is believed to have happened in the fall, the beginning of the new agricultural cycle. But the people Israel date their calendar from the Exodus, which happened in the spring (cf. Exod. 12:2 designating the month of the Exodus as the first month of Israel’s calendar).

[Etz Hayim: Torah and Commentary, pp. 727-728]

תִּשְׁרֵי (transliterated Tishrei or Tishri) is described in the Torah as the 7th month of the Hebrew year.

Timing: Early fall (September–October on the Gregorian calendar)

15th of Sh’vat – Tu BiShvat – New Year for Trees

This marks the beginning of the agricultural cycle for trees in Israel. It’s when the tithes from fruit trees were calculated. Today, it’s celebrated as an environmental and agricultural holiday, often called the “Jewish Arbor Day.”

שְׁבָט (transliterated Sh’vat or Shevat) is described in the Torah as the 11th month of the Hebrew year.

Timing: Winter (January–February on the Gregorian calendar)

1st of Nisan – New Year for Kings and Festivals

This is when the reigns of Jewish kings were counted (regardless of when they actually began ruling — it was “bumped up” to Nisan). It’s also significant for the religious calendar, as Nisan is the month of Passover and marks the Exodus from Egypt. In the Torah, Nisan is considered the first month of the year.

Timing: Spring (March–April on the Gregorian calendar)

נִיסָן (transliterated Nisan or Nissan) is described in the Torah as the 1st month of the Hebrew year.

1st of Elul – New Year for Tithing Animals

This was the cut-off date for determining which animals had to be tithed in Temple times. Animals born before and after Elul 1 were counted separately for the tithe.

Elul (אֱלוּל) is described in the Torah as the 6th month of the Hebrew year.

Timing: Late summer (August-early September on the Gregorian calendar)

Conclusion

You may notice that the Bible speaks of Rosh Hashanah as occurring on the first day of the seventh month. The first month of the Jewish calendar is Nissan, occurring in March and April. Why, then, does the Jewish “new year” occur in Tishri, the seventh month?

Judaism has several different “new years,” a concept which may seem strange at first, but think of it this way: the American “new year” starts in January, but the new “school year” starts in September, and many businesses have “fiscal years” that start at various times of the year.

[via Rosh Hashanah – Judaism 101 (JewFAQ)]

תִּשְׁרֵי (transliterated Tishrei or Tishri) is the 7th month of the Hebrew year, is 30 days long, and corresponds to September or October on the Gregorian calendar.

The holiday that occurs on the 1st day of Tishrei is called Rosh Hashana, the Jewish New Year. Rosh Hashanah is a major holiday.

The first day of Tishrei is not considered Rosh Chodesh. Rosh Chodesh is a minor holiday that occurs at the beginning of every month on the Hebrew calendar. In the case of Tishrei, the major holiday of Rosh Hashana takes precedence.

Later in the month we observe Tzom Gedaliah on the 3rd, Yom Kippur on the 10th, Sukkot (from the 15th-21st), and Shmini Atzeret (on the 22nd) and Simchat Torah (on the 23rd in the Diaspora).

For more info, read The Month of Tishri – Judaism 101.

Asara B’Tevet / עֲשָׂרָה בְּטֵבֵת, the tenth day of the Hebrew month of Tevet, is a minor fast day in Judaism. The fast commemorates the siege of Jerusalem.

Although the Tenth of Tevet is an annual observance on the Hebrew calendar, the date can fall during December or January on the Gregorian calendar. In some Gregorian years, there is no observance of the fast. In other Gregorian years, the fast is observed twice.

For example, the Tenth of Tevet does not occur at all in during the Gregorian year 2024. The fast for Hebrew year 5785 will be observed in January 2025, and the Asara B’Tevet 5786 observance of the fast will be in occur in December 2025.

To illustrate further, consider the following 8-year table:

Hebrew Date	Gregorian Date
10 Tevet 5780	Tuesday, January 7, 2020
10 Tevet 5781	Friday, December 25, 2020
10 Tevet 5782	Tuesday, December 14, 2021
10 Tevet 5783	Tuesday, January 3, 2023
10 Tevet 5784	Friday, December 22, 2023
10 Tevet 5785	Friday, January 10, 2025
10 Tevet 5786	Tuesday, December 30, 2025
10 Tevet 5787	Sunday, December 20, 2026