Moon Phase Software

Moon tools

Moon calculation conventions

Each tool resolves a local civil input to one UTC instant before it evaluates the requested lunar state or event. The guides below explain the reference frame, units, event ordering, and display conventions that change how each result should be read.

Four physical astronomy instruments arranged on a navy workbench

Four calculation families

Choose the method behind the result

  1. 01Moon Phase Calculation MethodsLearn how geocentric phase angle, illuminated fraction, lunar age, and principal Moon phases are calculated for one exact UTC instant online.
  2. 02Moon Distance Calculation MethodsLearn how geocentric Moon distance, apparent angular size, and the adjacent perigee and apogee events are calculated for an exact instant online.
  3. 03Moon Position Calculation MethodsLearn how observer coordinates produce topocentric Moon position, altitude, azimuth, moonrise, moonset, transit, and refraction results online.
  4. 04Lunar Eclipse Calculation MethodsLearn how global lunar eclipse peaks, contact times, phase durations, event types, and umbral obscuration are calculated around an exact instant.

Time convention

From local time to one instant

  1. 01Read fields

    Date, 24-hour time, and optional observer coordinates.

  2. 02Resolve the zone

    Apply the selected IANA zone to the local civil time.

  3. 03Fix the instant

    Convert the resolved value to one unambiguous UTC instant.

  4. 04Evaluate

    Calculate state, geometry, local position, or adjacent events.

Display conventions

Read each value in its own frame

Phase and distanceEarth-centred geometry for an exact instant.

PositionObserver-centred output using an ideal sea-level horizon.

EclipsesGlobal shadow events; use position separately for a local horizon check.

RoundingDecimals are selected for readable comparisons between instants.