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The Moon’s clock · an interactive experiment

See the tithis in action

Watch thirty tithis and the Moon’s visible phase move through one complete cycle, one 12-degree change at a time.

Watch for the fourth tithi.

Gajajī will celebrate Caturthī in each half of the lunar cycle.

The Moon–Sun angle divided into thirty tithisA simplified Earth-centered teaching diagram. The Moon moves around Earth while the angle from the Sun advances through thirty equal twelve-degree intervals.SunEarthMoonMoon–Sun angle 6°
Earth-centered teaching view · sizes and distances are not to scale

The view from Earth

near New Moonabout 0% illuminated

The visible phase is a clue. The tithi is determined by the measured Moon–Sun angle.

Tithi 1 of 30
Śukla Pratipadābright, waxing half
0°–12°
Loop speed

What this model teaches

The phase and the tithi come from the same changing relationship.

Sunlight always illuminates half of the Moon. As the Moon’s position changes relative to Earth and the Sun, we see different portions of that illuminated half. A tithi is more exact than a phase name: it is one of thirty equal intervals in the Moon–Sun angle as measured from Earth.

A simplified teaching model

This simplified diagram uses a smooth, repeatable cycle for conceptual study. Live reports calculate a specific date and location from astronomical data.