How we calculate

Every time, date and verdict on The Moon Tracker is calculated, not copied from another website. This page explains the methods, the published sources behind them and how we check the results.

Positions of the Sun and Moon

Positions come from Astronomy Engine 2.1.19, an open-source library by Don Cross that agrees with the US Naval Observatory’s NOVAS software to within one arcminute. We compute the sky as seen from the chosen town, using its latitude, longitude and height above sea level, and show every time in that town’s own time zone, including daylight saving.

Rise, set and twilight

Sunrise, sunset, moonrise and moonset are the moments the top edge of the disc meets a flat, clear horizon, with standard atmospheric refraction. Civil, nautical and astronomical twilight begin when the Sun is 6°, 12° and 18° below the horizon. Evening golden hour starts when the Sun is 6° above the horizon, and blue hour when it is 4° below. Times in our tables are rounded to the nearest minute.

Checked against the US Naval Observatory

For 1 November 2026, local time, our times and the US Naval Observatory’s agree to the minute in 23 of 24 cases; the other differs by one minute.

Each cell: The Moon Tracker / US Naval Observatory. New York changes from daylight time to standard time that morning. Checked on 19 October 2026.

The new crescent (hilal)

For each evening after the new moon (conjunction) we calculate the Moon’s age, the time between sunset and moonset, and the crescent’s geometry at the best time to look, which is sunset plus four ninths of that lag. Three methods are compared side by side:

• International Astronomy Center criterion (Odeh 2006), zones A to D: visible by eye; visible with optical aid and possibly by eye; visible with optical aid only; not visible even with optical aid.
• UK Nautical Almanac criterion (Yallop 1997), categories A to F, used by HM Nautical Almanac Office.
• Umm al-Qura rule, used for the Saudi calendar: at Mecca, the conjunction happens before sunset and the Moon sets after the Sun.

Our results reproduce the published HM Nautical Almanac Office visibility for 19–20 March 2026 and the International Astronomy Center report for 11–12 October 2026.

Hijri dates

Hijri dates use the Umm al-Qura calendar as built into modern web browsers. For example, it gives 1 Jumada al-Awwal 1448 as 12 October 2026 and 29 days for Jumada al-Thani 1448. Countries and communities that follow a sighting may begin a month a day earlier or later.

Eclipses

Eclipses are found with Astronomy Engine. Local contact times come from the geometry of the Moon, the Sun and Earth’s shadow; Earth’s shadow is enlarged by 2% for its atmosphere, as is standard practice. Dates, types and times for 2026–2028 agree with NASA’s eclipse catalogue by Fred Espenak and Jean Meeus to within about a minute: for example, totality on 3 March 2026 from 11:04 to 12:03 UT.

Hindu, Chinese and Hebrew calendars

• Tithi: each tithi is 12° of the Moon’s movement away from the Sun. Solar months (sankranti) use the sidereal zodiac with the Lahiri ayanamsa (23.853° at 2000, increasing by 50.29″ a year). Karwa Chauth is the Krishna Paksha Chaturthi after the full moon that follows Tula sankranti, with moonrise during the chaturthi.
• Chinese lunar calendar: months begin on the day of the new moon in China Standard Time (UTC+8); the month containing the winter solstice is the 11th, and in a 13-month year the first month without a principal solar term is the leap month.
• Hebrew calendar: dates and Rosh Chodesh come from the Hebrew calendar built into web browsers. The Kiddush Levanah window is counted from the astronomical new moon; many communities count from the traditional molad, which can differ by some hours.

Towns

Towns, heights and time zones come from GeoNames, using the 26,435 places with more than 15,000 people.

What the calculations do not include

Weather, haze, hills and buildings, and the eyesight of observers are not included. The Moon Tracker gives calculations, not sightings, and it is not a religious authority. For the start of a month, a fast or a prayer, follow the authority your community trusts.

Sources

• Astronomy Engine, Don Cross: github.com/cosinekitty/astronomy
• US Naval Observatory, Astronomical Applications: aa.usno.navy.mil
• Odeh, M. Sh. (2006). New criterion for lunar crescent visibility. Experimental Astronomy 18, 39–64.
• Yallop, B. D. (1997). A method for predicting the first sighting of the new crescent Moon. NAO Technical Note No. 69, HM Nautical Almanac Office.
• International Astronomy Center: astronomycenter.net
• NASA eclipse website, Fred Espenak: eclipse.gsfc.nasa.gov
• GeoNames: geonames.org

Found a difference from an official source? Please tell us at contact@themoontracker.com.