Zmanim · The moments of the day
What is alot hashachar?
Alot hashachar (the break of dawn) is the very first light on the horizon, while the sky is still dark. It marks the start of the halachic day for a number of mitzvot, and it is reckoned by how far the sun still sits below the horizon where you live.
The first light, while it is still night
Before the sun is anywhere near rising, a faint light spreads at the edge of the sky. That first glimmer is עלות השחר, the break of dawn — the earliest boundary of the Jewish day. A number of mitzvot that belong to daytime can already be fulfilled from this moment, even though, to the eye, it is still night. It is the hinge on which the night turns toward the day.
Where this is taught
The Talmud, in tractate Berakhot (26a), weighs dawn as a boundary for the day's prayers, and in Pesachim (94a) the sages measure the distance of dawn from sunrise itself. Because dawn is not a single worldwide instant, the tradition fixes it by the sun's angle beneath the horizon — a depth of light rather than a number on a clock — which is why it falls at a different moment in your city than in another.
What to do
For most days, you will not act at dawn itself — but knowing it grounds the hours that follow. If a fast day begins for you, or you keep an unusually early schedule, this is the line that matters. Rather than guessing at a dark window, let the app tell you when alot hashachar actually falls where you are, so the day begins on a boundary you can trust.
Source: Talmud, Berakhot 26a; Pesachim 94a.
Kimá — the Jewish clock: your city's zmanim and candle times — calculates dawn for your exact place and date, so the first light of the day is one you can actually find.
Open Kimá