The Moon and the Islamic Calendar: Phase, Crescent and Dates

What a new moon calculation tells you

Astronomical conjunction marks the beginning of a phase cycle. The Moon’s changing position relative to the Sun produces the waxing and waning phases shown in the sky view. The first visible waxing crescent occurs later than conjunction.

The Tehran view shows the selected time, the Moon’s phase, its geometric altitude and azimuth, and the surrounding Sun and Venus positions. These measurements help describe where to look and how the bodies are arranged.

What establishes a religious month?

Qur’an 2:189 connects crescents with time and pilgrimage, and 10:5 connects lunar stages with reckoning years and time. The month-establishment rules used by a religious authority determine what evidence is accepted. The source chain linked in this app includes sighting, reliable evidence and completion of thirty days.

This annual edition retains the lunar dates printed in Iran’s calendar. The horizon calculation does not declare that a crescent was observed or accepted by an authority.

Why the crescent does not point in one permanent direction

The Moon’s compass direction depends on the observer, date and time. Its altitude describes height above the horizon; azimuth describes direction around it. The Tehran view uses north as 0°, east as 90°, south as 180° and west as 270°.

The calculation uses a flat horizon. Mountains, weather and actual visibility need further consideration when observing. The app’s comparison window for the Moon and Venus is a declared geometry setting rather than a month-start rule.

Explore the religious date beside the sky

Choose a date in Moon & Why to read the published lunar observance alongside the selected sky. The same page explains the historical Tephras comparison, the author’s Moon–Venus proposal and the relevant textual sources. Each remains visible in its own part of the reading.