1. It Marks the Start of the Babylonian Siege

The 10th of Tevet (known as Asara B’Tevet in Hebrew) is a fast day, marking the day (in the year 3336 from Creation, or 425 BCE) when the troops of Nebuchadnezzar of Babylonia surrounded Jerusalem, beginning a 30-month siege, which ended with the destruction of the city, the ruin of the Holy Temple, and death and enslavement of many of her citizens. This is seen as the catalyst for the future exiles and a cataclysmic event from which we have never fully recovered, because even when the Second Temple was finally built, it never returned to its full glory.

Read: The Destruction of the First Holy Temple

2. The Date Was Recorded by Ezekiel

Ezekiel tells us: “The word of the L‑rd came to me in the ninth year,1 in the tenth month, on the tenth of the month, saying: ‘Son of man, write for yourself the name of the day, this very day; the king of Babylon has besieged Jerusalem on this very day.’ ”2

What is the 10th month? The month of Tevet, the 10th month from the joyous springtime month of Nissan, which G‑d chose to be the “head” of the sequence of Jewish months.3

Read: The Prophet Ezekiel

3. The Fast Is Listed by Zechariah

The Prophet Zechariah records the following message he received from G‑d: The fast of the fourth [month], the fast of the fifth [month], the fast of the seventh [month], and the fast of the tenth [month] shall be for the house of Judah for joy and happiness . . .”4

In this uplifting prophecy, we are told that the tragic dates on the fourth, fifth, seventh and tenth months on the Jewish calendar will one day be transformed from fasting to feasting, from mourning to celebration.

What is the “fast of the 10th month”? The Tenth of Tevet, of course.

Watch: The Hidden Good

4. We Fast From Daylight to Nightfall

Like 17 Tammuz, the Fast of Gedaliah (3 Tishrei) and the Fast of Esther (13 Adar), this fast begins at dawn and concludes at nightfall, when three medium-sized stars appear in the sky.

Since these fasts are seen as somewhat less strict than Yom Kippur and 9 Av (which start at sundown the day before), there is room for leniency for expectant and nursing mothers, and others with specific medical conditions.

Read: Jewish Fast Days FAQ

5. It’s the Shortest Fast (in Northern Hemisphere)

In the Northern Hemisphere, the shortest day of the year occurs between Dec. 20 and 23. Observed in December or early January, 10 Tevet is the shortest fast day on the Jewish calendar, often just 11 hours long from start to finish. Conversely, in Sydney, Australia, the fast can be more than 16 hours long.

Check Out the Fast Times for This Year

6. You Can Get Up Early For a Cuppa Joe

Since the fast begins relatively late, it is entirely possible to get up early to get an extra shot of caffeine and a bite to eat. However, if you wish to do so, be sure to have this in mind before you go to sleep the night before, otherwise the fast may halachically begin for you when you wake up, even if it is technically before the start time.

Read: Waking Up Early to Eat Before a Fast

7. It Is the Only Fast That Can be on Friday

Unique among Jewish fasts, 10 Tevet is observed even when it falls on a Friday, though it interferes somewhat with Shabbat preparations, causing us to fast all the way until we make kiddush on Friday evening.5

Read: How Can 10 Tevet Interfere With Shabbat?

8. It Also Commemorates the Translation of the Torah Into Greek...

Determined to have the Torah translated into Greek (following an unsuccessful attempt 61 years earlier), the ruling Alexandrian-Greek emperor Ptolemy gathered 72 Torah sages, had them sequestered in 72 separate rooms, and ordered them to each produce a translation of the Torah. On the 8th of Tevet of the year 3515 (246 BCE), they produced 72 identical translations. This was miraculous, especially since there were 13 places where the translators intentionally diverged from the literal translation.6

Despite the miracles, the rabbis viewed this event as one of the darkest days in Jewish history, comparing it to the day the Golden Calf was made.

Read: Why the Translation Was a Bad Thing

9. ...As Well As the Passing of Ezra

Ezra the Scribe passed away on 9 Tevet of the year 3448 (313 BCE), exactly 1,000 years after the giving of the Torah on Mount Sinai.

Ezra led the return of the Jewish people to the Land of Israel after the Babylonian exile, oversaw the building of the Second Temple, and helped put a stop to the wave of intermarriage that afflicted the Jews at that time. As head of the Great Assembly, he canonized the 24 books of the Holy Scriptures (Tanach) and legislated a series of laws and practices, including formalized prayer, guaranteeing the continuation of authentic Judaism among the Jewish people to this very day.

Read: Ezra the Scribe

10. We Say Selichot and Other Special Prayers

As part of the morning services, we add Selichot, a litany of prayers and poetic liturgy, lamenting the sad events of this day—and of our history in general—and asking G‑d to forgive our sins.

Other changes to the daily prayers include special insertions in the Silent Prayer, an elongated Tachanun service, and Torah readings in the morning and afternoon.

Read: How We Pray on 10 Tevet