month (synodic) Unit Converter

Definition of month (synodic) unit

A synodic month is the average interval between two successive identical lunar phases, usually new moons, as observed from Earth. It lasts approximately 29.53059 mean solar days and governs the Moon’s changing illumination cycle.

History of month (synodic) unit

The concept of the synodic month emerged from ancient observations of the repeating lunar phases, which provided one of humanity’s earliest practical calendars. Babylonian, Egyptian, Greek, Chinese, Islamic, and other traditions tracked new moons to organize ritual, agricultural, and civic life. The term derives from Greek synodos, meaning “meeting” or “conjunction,” referring to the Moon’s apparent return to alignment with the Sun. Unlike the sidereal month, measured against distant stars, the synodic month changes slightly because Earth and Moon continually move around the Sun.

Applications of month (synodic) unit

Today, the synodic month is used in lunar and lunisolar calendars, including the Islamic and Hebrew calendars, to determine month boundaries and religious observances. Astronomers and educators use it to predict phases, eclipses, and tides. In everyday language, “month” often approximates this cycle, although civil calendar months are assigned fixed or variable lengths.

Complete list of month (synodic) unit conversion