How the Hebrew calendar generator computes candle lighting and tzeit hakochavim

Finding the year from Tishrei through Elul

The Hebrew year begins on Rosh Hashanah, the first of Tishrei. Organizing pages by Hebrew month keeps each month together instead of dividing it across Gregorian pages. The existing daily dataset maps Gregorian dates from 2020 through 2036 to their Hebrew equivalents. To build a year such as 5786, the tool filters for that Hebrew year, sorts the dates, and groups consecutive entries by month. The grouping also separates Adar I and Adar II in leap years. A complete year requires the date immediately before it and the date immediately after it to be present in the dataset. Excluding the partial years at the edges leaves 16 usable Hebrew years.

Entering a Gregorian year

A Hebrew year spans parts of two Gregorian years: it begins with Rosh Hashanah in September or October and ends with Elul in the following year. If you enter 2026, the tool finds the Hebrew year whose Rosh Hashanah falls in 2026 and displays the range "2026-2027", with an explanation that the calendar continues into the second year. It does this by finding the Tishrei 1 entry in the daily dataset and reading its Hebrew year. Entering a Hebrew year directly leads to the same calendar-building function.

Calculating candle-lighting, Havdalah, and tzeit hakochavim times

Sunset depends on the date, latitude, and longitude, so its calculation waits until you choose a location. The Hebrew calendar generator from Orisod runs a solar-position library in the browser to calculate the times used in the PDF. These live calculations cover weekly Shabbat and the relevant Yom Tov dates, including weekdays, for candle-lighting and Havdalah. The tool uses the applicable timing rules and the selected tzeit hakochavim method: fixed minutes after sunset or a solar-depression angle. A single fixed offset from sunset does not describe both methods. The holiday and Hebrew-date tables can be prepared in advance, but the solar calculations need your chosen coordinates.

Two methods for tzeit hakochavim

Tzeit hakochavim, the emergence of the stars that marks the end of Shabbat or a holiday, is defined differently across communities. One method uses a fixed interval after sunset, commonly 42, 50, or 72 minutes. The other calculates when the sun reaches a specified angle below the horizon, commonly 3.7, 4.61, 6.5, or 8.5 degrees. The results can differ substantially with location and season. Both methods are available in the dropdown so you can select the one used by your community.

Choosing a location and time zone

City search retrieves a stored latitude, longitude, and time zone together. Browser geolocation uses your current coordinates and reuses the time zone reported by your device. You can also enter coordinates manually, which is useful for a place you are not visiting or one absent from the city list. Manual entry requires a separate time-zone selection: the tool does not bundle the geographic boundary data needed to map arbitrary coordinates to a time zone. These location options supply the solar calculations; you select Israel/Diaspora mode manually.

The weekly Torah portion in Israel and the Diaspora

Parashat HaShavua follows an annual reading cycle. Portions such as Vayakhel-Pekudei may be combined or separated according to the Hebrew calendar, and a major holiday on Shabbat replaces the regular weekly portion with its special reading. The tool resolves the weekly portion through @hebcal/core using its il flag to match your manual Israel/Diaspora selection. This accounts for weeks when the two reading cycles diverge. The same selection also governs differences in Chol HaMoed length and whether Shemini Atzeret and Simchat Torah share a day. On a Shabbat with a holiday reading, the displayed holiday name identifies the occasion in place of a regular weekly portion.

Preparing and checking your calendar

You can view the calendar before choosing a location. Hebrew dates, holidays, day colors, and the weekly Torah portion are available without coordinates. Choose a location when you want candle-lighting, Havdalah, and tzeit hakochavim times.

Use the calculated times as a reference. Sunset, candle-lighting, Havdalah, and tzeit hakochavim calculations are estimates, not a religious ruling. Elevation, the visible horizon, atmospheric conditions, high latitudes, and differences between calculation methods can affect the results. Confirm the times and method with your rabbi or local community before relying on them for observance.

Add photos and custom events to the Hebrew months. These features work as they do in the general Calendar generator, with your content arranged on Hebrew-month pages.

The calendar is generated locally in your browser. The Hebrew calendar generator performs its stored-city lookup, sunset calculations, and PDF generation there. Your calendar photos and custom events are not uploaded to a server for that processing.

Before printing, check the Hebrew year, location, time zone, and manual Israel/Diaspora selection. The location and tzeit hakochavim method affect the displayed times, while Israel/Diaspora mode determines the applicable holiday pattern and weekly reading cycle. Confirm the timing method with your rabbi or local community.