Shabbat Candle Lighting & Havdalah Time Calculator
What this calculator estimates
This page estimates two widely used Shabbat-related times for a given location and date:
- Candle lighting (Friday): commonly set to a fixed number of minutes before local sunset (often 18 minutes in many communities).
- Havdalah (Saturday night): commonly set to a fixed number of minutes after local sunset (often 42 minutes as a practical approximation of nightfall in some communities).
The calculator uses your Friday date, latitude, longitude, and time zone offset to estimate local sunset, then applies these offsets (“buffers”) to produce candle lighting and havdalah estimates.
Inputs you’ll need (and common pitfalls)
- Date: choose the Friday you care about. Havdalah is computed for the following day (Saturday).
- Latitude: valid range −90 to +90. North is positive; south is negative.
- Longitude: valid range −180 to +180. East is positive; west is negative (e.g., New York is about −74).
- Time zone offset from UTC (hours): for example, UTC−5 (Eastern Standard Time), UTC+2 (Israel Standard Time). If daylight saving time is in effect, the offset changes (e.g., UTC−4 instead of UTC−5).
Tip: If your results look off by exactly one hour, the most common cause is a DST mismatch in the UTC offset.
How the estimate is computed (high-level)
Sunset time depends on Earth–Sun geometry and your position on Earth. At a high level, the steps are:
- Convert the selected date into a day-of-year value used by standard solar position approximations.
- Estimate the Sun’s apparent position (declination and right ascension) for that day.
- Compute the hour angle at sunset for the given latitude using a standard “sunset zenith” constant that approximates refraction and the Sun’s radius (often near 90.833°).
- Convert that to a civil clock time, then shift from UTC using your entered offset.
- Apply community-style offsets: candle lighting = sunset − 18 minutes, havdalah = sunset + 42 minutes (unless your implementation uses different defaults).
Core formulas (conceptual)
The key geometric step is solving for the hour angle H at which the Sun reaches a chosen zenith distance Z at your latitude φ, given the Sun’s declination δ. A common rearrangement is:
Once H is known, it is converted into time (15° per hour), then adjusted for longitude and the equation-of-time approximation to obtain an estimated local sunset. The Shabbat-related times are then simple offsets from that sunset:
- Candle lighting = sunset time − 18 minutes (common default)
- Havdalah = sunset time + 42 minutes (common default)
Interpreting the results
- If the page shows a Friday candle lighting time, treat it as the latest target time to have candles lit before Shabbat begins (many people aim a few minutes earlier).
- If the page shows a Saturday havdalah time, treat it as an estimate of when Shabbat has ended under a “minutes after sunset” convention. Communities vary in how they define nightfall (tzeit), so this may differ from synagogue schedules.
- If you see unusual outputs (very early/late sunsets), double-check the longitude sign (east vs. west) and the UTC offset.
Worked example
Scenario: You enter a Friday date, a location near Jerusalem (latitude about 31.78, longitude about 35.21), and a UTC offset of +2 (or +3 during DST).
- The calculator estimates Friday sunset for that latitude/longitude and date.
- It computes candle lighting as sunset minus 18 minutes.
- It estimates Saturday sunset and computes havdalah as sunset plus 42 minutes.
If your local community publishes candle lighting at a different offset (e.g., 20, 30, or 40 minutes before sunset) or uses a different definition for havdalah/nightfall, you should follow that schedule rather than a generic offset.
Common conventions compared
| Item | Common rule-of-thumb | What it’s approximating | Why it may differ locally |
|---|---|---|---|
| Candle lighting | 18 minutes before sunset | Practical “before sunset” margin | City/community minhag; seasonal or municipal schedules; local rabbinic guidance |
| Havdalah | 42 minutes after sunset | Rule-of-thumb for nightfall | Different definitions of tzeit (stars out); latitude/season; community practice |
| Sunset itself | Calculated (zenith ≈ 90.833°) | Accounts for refraction + Sun’s radius | Elevation, atmospheric conditions, and algorithm choice can shift results slightly |
Limitations and assumptions (please read)
- Not halachic psak: This is an estimator. Halachic times depend on definition choices (e.g., sunset vs. shkiah, various tzeit methods) and local custom.
- Offsets are conventions: The 18-minute (candle lighting) and 42-minute (havdalah) buffers are common but not universal. Many communities use different numbers.
- DST handling: You provide the UTC offset. The calculator does not automatically know whether daylight saving time applies to your date/location.
- Elevation not modeled: Local horizon height and observer elevation can shift apparent sunset by a few minutes.
- Extreme latitudes: Near the Arctic/Antarctic circles, standard sunset formulas and “minutes after sunset” conventions may become unstable or non-applicable in some seasons.
- Atmospheric variability: Refraction varies with pressure/temperature; standard constants approximate average conditions.
Best practice: When in doubt, confirm with your local synagogue schedule or a trusted Jewish calendar for your community.
Method note (lightweight attribution)
The solar position and sunset estimate follow widely used civil/NOAA-style approximation steps (mean anomaly, ecliptic longitude, declination, hour angle, and time conversion). Halachic timekeeping may use different definitions and should be verified against local practice.