Holidays in Israel

Official national public holidays. Regional and religious observances may vary by area.

About Time in Israel

The Secret That Had to Be Published

For most of antiquity, a new Hebrew month began only when the Sanhedrin in Jerusalem had heard the testimony of witnesses who had personally seen the crescent moon, after which the news was carried outward by chains of hilltop signal fires and, later, messengers, to Jewish communities across the region. The system depended on a functioning central court in the land of Israel, and by the fourth century CE that had become politically untenable: Roman persecution under the emperor Constantius II made it dangerous, and eventually impossible, to keep gathering witnesses and dispatching couriers in the traditional way.

According to a tradition first recorded by the tenth-century scholar Hai Gaon, the patriarch Hillel II responded around 358 or 359 CE by publishing rules for calculating the calendar mathematically rather than by observation, a closely guarded process until then known as the secret of intercalation. The reform fixed a nineteen-year cycle in which seven years receive an extra month, keeping the lunar calendar in step with the solar seasons without any need for local sightings or messengers. Modern historians examining later evidence, including a ninth-century letter recovered from the Cairo Geniza that shows holidays still being observed on dates the current system would not produce, argue that the calendar did not reach its precise present-day form until several centuries after Hillel, closer to the 920s CE. Whatever its exact date of completion, the resulting fixed calendar, still in use essentially unchanged, replaced observation with arithmetic and let Jewish communities scattered across the world mark the same festivals on the same day without waiting for news from Jerusalem.

An Hour That Grows and Shrinks With the Season

Jewish religious law measures much of the day not in the fixed sixty-minute hours of a clock but in units called sha'ot zemaniyot, proportional or seasonal hours, each defined as exactly one-twelfth of the interval between sunrise and sunset. In practice this means an "hour" governing when morning prayers may be recited or when a fast must end stretches to as much as seventy-five minutes on a long midsummer day and shrinks to under fifty minutes in December, since the boundaries are anchored to the sun's actual position rather than to a uniform clock. Deadlines derived this way, known collectively as zmanim, govern dozens of practices, from the latest permissible time to recite the morning Shema to the moment three stars must be visible before a fast or the Sabbath can end, and different rabbinic authorities have historically disagreed by minutes over exactly how dawn, sunset or "nightfall" should be defined for these calculations.

Because the underlying astronomy, not tradition, is what actually changes from place to place, this centuries-old system has translated unusually smoothly into software: contemporary calculation engines built on NOAA's published solar-position algorithms compute a full day's zmanim for any coordinates and date, and are distributed today as open-source code libraries alongside ordinary weather and mapping tools, quietly running the same seasonal-hour logic described in medieval rabbinic texts on modern phones and prayer-time apps.

The Fast That Argued With the Clock

Because Yom Kippur falls on a fixed date in the lunar Hebrew calendar, its position relative to the Gregorian calendar drifts across several weeks in September and October from year to year. For decades this created a recurring political headache: under the law inherited from the British Mandate and later administered by the Interior Ministry, Israel's summer clocks were typically turned back to standard time on the Sabbath before Yom Kippur, a change religious parties argued made the daylong fast, which runs from sunset to nightfall, feel shorter by folding an extra hour of darkness into the evening. Critics on the secular side countered that ending daylight saving time so early each autumn, sometimes as much as six weeks before most of Europe, needlessly increased electricity use during the remaining weeks of warm weather, and the annual argument over the exact date became a recurring flashpoint between religious and secular parties in the Knesset.

The matter was largely settled by a law passed on 5 November 2012, which extended daylight time to a fixed 193-day period running from the Friday before the last Sunday in March to the first Sunday after 1 October, overriding the religious calendar's influence on the switch date except for a specific carve-out if that October date happened to coincide with Rosh Hashanah. The reform was projected to save the Israeli economy roughly 300 million shekels a year in reduced electricity costs, and it left Israel, for the first time, observing daylight saving on a schedule close to the rest of Europe rather than one keyed to the drifting date of a religious fast.

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