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Frequently Asked Questions

Welcome to our general site FAQ. Here you will find direct answers regarding our free tools, calculation methods, data privacy, site support, and calendar rules. Use the topic links below to navigate to specific question categories.

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General Site Usage & Costs

Are the Jewish calendar tools free to use?

Yes. All interactive tools on JewishCalendarTools.com are free to use. There are no paywalls, hidden fees, premium tiers, or paid subscriptions for any of our calculation features.

How is the site supported?

JewishCalendarTools.com is designed to be supported by unobtrusive advertising after launch. Ad revenue allows us to maintain server operations and update open source software libraries while keeping all tools freely accessible to the public.

Do I need to create an account or sign up?

No. You do not need an account, password, or email registration to use any of our six core tools. All calculators function instantly in your web browser.

Do I need to install software or an app?

No. All tools run directly inside modern desktop and mobile web browsers. No app store downloads or browser plugins are required.

Privacy & Data Security

Is my personal data stored on your servers?

No. We prioritize visitor privacy. All date conversions, birthday calculations, Yahrzeit lookups, and location choices take place entirely within your browser or via stateless real-time API requests. We do not store, log, or compile database records of personal names, dates of birth, or dates of passing entered into our calculators.

Do you track my location?

We do not track your location without your explicit action. When looking up Shabbat times, you can type any city name manually. If you choose to enable browser location lookup, your geographic coordinates are used strictly to calculate local sunset times and are never sold or retained.

Accuracy & Calculations

How accurate are the Shabbat and holiday calculations?

Our tools use astronomical solar positioning algorithms derived from NOAA equations combined with official IANA time zone rules and verified geographic coordinates. Calendar conversions and holiday dates utilize the audited open source @hebcal/core engine.

How are time zones and Daylight Saving Time handled?

Time zone rules and seasonal Daylight Saving Time shifts update dynamically using the global IANA Time Zone Database (TZ Database). This ensures accurate local times across changing daylight savings boundaries worldwide.

Where can I learn more about your code and algorithms?

We believe in full transparency. Read our complete calculation methodology to learn about our algorithms, and inspect our data sources page for open source licensing and library attribution.

Sunset & Calendar Rules

Why do Jewish dates begin at sunset rather than midnight?

In Jewish tradition, the day starts at sundown based on the biblical creation narrative (“and there was evening and there was morning, one day”). As a result, every Jewish date spans parts of two consecutive civil calendar days.

How does “after sunset” affect calculator results?

If an event (such as a birth, death, or conversion) took place after sunset on a civil date, it falls on the subsequent Hebrew date. Selecting “after sunset” in our calculators automatically advances the Hebrew date by one day.

What happens in high latitude cities with extreme sunset times?

In cities far north or south during midsummer, sunset occurs very late in the evening or not at all. Our calculators detect these extreme astronomical conditions and report when standard calculations are mathematically unavailable, advising users to consult local rabbinic guidance rather than generating an arbitrary result.

Israel versus Diaspora Differences

Why do holiday durations differ between Israel and the Diaspora?

In Israel, major biblical holidays (such as Passover, Shavuot, and Sukkot) are observed for seven days, one day, and seven days respectively. In the Diaspora, an extra day (Yom Tov Sheni Shel Galuyot) is added due to ancient historical communications delays when declaring the new moon.

Why do Torah readings sometimes differ between Israel and Diaspora?

When a holiday’s second day falls on Shabbat outside Israel, Diaspora synagogues read the special holiday Torah portion while Israeli synagogues resume the regular weekly cycle. This creates a one-week offset in weekly Torah readings that can last for several weeks until reading cycles realign.

Religious Guidance & Rabbinic Authority

Is JewishCalendarTools.com a rabbinic authority?

No. JewishCalendarTools.com is an educational and computational web resource, not a rabbinic authority or halachic court. Our tools provide accurate astronomical and mathematical data based on documented standard customs.

Who should I consult for personal observance questions?

For specific religious rulings, complex edge cases, family traditions, or personal halachic decisions, we strongly advise consulting a qualified Orthodox rabbi or local spiritual authority.

Still Have Questions?

If you have additional technical feedback, bug reports, or site questions: