Moon Phase Calculator & Moonrise Times

About the Moon Phase Calculator & Moonrise Times

See the Moon for any date and time from 1600 to 2400 — today, a birthday or a date in history: its phase, how much of the disc is lit, its age in days since the new moon, its distance and apparent size (with supermoon and micromoon marked), the constellation it is in, and the dates and times of the next new moon, first quarter, full moon and last quarter.

For your city or location you also get moonrise, moonset, the time the Moon is highest and where it is in the sky at the chosen time, and the Moon can be drawn tilted exactly as it looks from your place. A monthly moon calendar, a table of every phase of the year (download it as CSV or add it to your calendar as an .ics file) and the next lunar eclipses — with whether you can see them — complete the picture. Everything is calculated in your browser with the astronomy-engine library.

Common uses

• Finding out the Moon’s phase on a birthday, wedding or historic date.
• Planning night photography, stargazing (dark skies near new moon) or a full-moon walk.
• Knowing when the Moon rises and sets and where to look for it.
• Checking upcoming supermoons, blue moons and lunar eclipses.
• Teaching why the Moon has phases and why it rises later each day.

How the phase is defined

The phases are set by the angle between the Moon and the Sun seen from the centre of the Earth, measured along the ecliptic: new moon at 0°, first quarter at 90°, full moon at 180° and last (third) quarter at 270°. These four are instants; on the calendar date when one happens the day takes its name. Between them the Moon is a waxing crescent, waxing gibbous, waning gibbous or waning crescent. The illuminated fraction is the share of the disc that is lit, and the Moon’s age is the time since the last new moon. A full cycle (synodic month) averages about 29.5 days (USNO, NASA), so most calendar months have one full moon; when a month has two, the second is called a blue moon.

Supermoon and micromoon

The Moon’s distance changes over each orbit from perigee (closest, about 363,300 km) to apogee (farthest, about 405,500 km) (NASA). “Supermoon” is not an official astronomical term; NASA notes it is typically used for a full Moon within at least 90 percent of perigee. This calculator takes the perigee and apogee of the orbit in which the full (or new) moon happens and calls it a supermoon when it is at least 90 % of the way from apogee to perigee, and a micromoon at most 10 % of the way. NASA says a supermoon can look up to 14 % bigger and 30 % brighter than the faintest full moon of the year.

Moonrise, moonset and the Moon’s position

Moonrise and moonset are when the Moon’s upper edge touches a level horizon, with the same standard refraction as for sunrise (USNO). The Moon rises on average about 50 minutes later each day, so some calendar days have no moonrise or no moonset, and near the poles the Moon can stay up or down all day. Positions are topocentric — seen from your place, not from the Earth’s centre — which matters for the Moon because it is close: its direction shifts by up to about a degree. The “as in your sky” view turns the drawing so that the lit edge points towards the Sun, as it does for an observer at the chosen place and time.

Sources

• US Naval Observatory, Phases of the Moon and Percent of the Moon Illuminated and Rise, Set, and Twilight Definitions; its phase and one-day data services are the reference for this tool’s tests (all within a minute or two).
• NASA Science, Supermoons and Moon Phases.
• NASA GSFC lunar eclipse tables (F. Espenak): the tool’s eclipse times match them to within a few minutes in its tests.
• J. Meeus, Astronomical Algorithms, 2nd ed., chapters 47–49 (Moon position, illumination and phases).
• D. Cross, astronomy-engine (MIT licence), the library that does the calculations, validated against JPL Horizons and NOVAS.
• GeoNames (CC BY 4.0) for the city list; the IANA time zone database built into your browser.

Limitations

• Moonrise and moonset assume sea level and a flat horizon; hills, buildings and unusual refraction can change what you see by several minutes.
• Dates are limited to 1600–2400. Long before or after today the Earth’s slowly changing rotation (ΔT) can only be estimated, so event times become less precise — by seconds in the 1600s and possibly minutes by 2400.
• Phase names on the calendar follow the local date in the chosen time zone, so a full moon can fall on different dates in different countries.
• Religious calendars that depend on the first sighting of the crescent (such as the Islamic calendar) or on lunar days (tithi) use their own rules; this tool shows the astronomical phases only.
• Eclipse visibility is judged from whether the Moon is above the horizon at greatest eclipse or during the partial phase; clouds, twilight and the faintness of a penumbral phase are not considered.
• Typed coordinates take the time zone of the nearest listed city within 300 km, otherwise the nautical zone of the longitude; check it in Coordinates and time zone near a border or at sea.

Privacy

Everything is calculated in your browser. If you press “Use my location”, your browser asks for permission and the coordinates are used on this page only — they are not sent to MySmartCoPilot or anyone else. The last city or coordinates you chose (never your device’s position) are remembered in this browser for next time; Reset forgets them.