Tzeis Hakochavim

Overview

Tzeis Hakochavim (צאת הכוכבים), meaning "emergence of the stars," marks the beginning of halachic night. This is when the day officially ends and a new Jewish day begins. It is defined as the time when three medium-sized stars are visible in the sky.

Talmudic Source

The Gemara Shabbos 35b states:

"When one can see one star it is still day; two stars, twilight; three stars, night."

The Gemara clarifies that these are medium stars — not the brightest stars that appear immediately after sunset, nor the faintest stars that require complete darkness.

The Standard Calculation: 8.5°

Based on observation in Eretz Yisrael, three medium stars become visible approximately 36 minutes after sunset at the equinox. This corresponds to when the sun is 8.5 degrees below the horizon.

Using degrees rather than fixed minutes allows the calculation to work at any latitude and season, as the actual visibility of stars depends on how far the sun has descended.

Different Opinions

Degree-Based Calculations

Time-Based Calculations

Rabbeinu Tam's Opinion

Rabbeinu Tam (Rabbi Yaakov ben Meir, 1100-1171) offers a fundamentally different understanding of nightfall.

The Gemara in Pesachim 94a states that from sunset to tzeis is the time to walk 4 mil (approximately 72 minutes) — the same duration as from alos hashachar to sunrise. But Shabbos 34b describes bein hashmashos as lasting "three-quarters of a mil" — which the poskim calculate as approximately 12-13.5 minutes after sunset.

Rabbeinu Tam reconciles this:

• Visible sunset (shkiah) is when the sun disappears below the horizon
• A "second shkiah" occurs 58.5 minutes later when the sun reaches a certain point
• Tzeis is 13.5 minutes after this second shkiah
• Total: approximately 72 minutes after visible sunset

Practice Today

Many communities — especially Hasidic and yeshivish — are stringent to wait 72 minutes for the end of Shabbos, following Rabbeinu Tam.

Rav Moshe Feinstein held that while the halacha technically doesn't follow Rabbeinu Tam, Bnei Torah should be stringent to wait 72 minutes for Motzei Shabbos. However, he also noted that in practice, even Rabbeinu Tam would agree that 50 minutes suffices in America since all stars are visible by then.

Halachic Applications

Tzeis Hakochavim is relevant for:

1. End of Shabbos and Yom Tov — When melacha becomes permitted
2. Beginning of fast days — For Yom Kippur and Tisha B'Av (which begin at sunset, the night before)
3. End of fast days — When one may eat
4. Beginning of Maariv — Earliest ideal time (though Plag HaMincha permits an earlier Maariv)
5. Krias Shema at night — Must be recited after tzeis
6. Sefirat HaOmer — Should be counted after tzeis
7. Beginning of the next Jewish day — For all date-dependent mitzvos
8. Havdalah — Should not be recited until tzeis

Which Time to Use?

Sources

• MyZmanim - Degrees Explanation
• Halachipedia - When Does Shabbat End
• Chabad.org - Rabbeinu Tam's Sunset
• Halacha Yomit - Time of Rabbeinu Tam
• RabbiKaganoff - It's About Time
• YCT Torah Library - Rabbeinu Tam's Two Sunsets