Moon Phase Software

Moon tools

Moon Phase Calculator for an exact date and time

Enter a local civil date, 24-hour time, and IANA time zone. The tool converts that instant to UTC and calculates the Moon's geocentric phase angle, illuminated fraction, lunar age, direction, and adjacent principal events.

Calculation input

Use an IANA name so historical daylight-saving rules are applied. The default is UTC.

Physical lunar phase wheel with a photographed Moon and engraved angle scale

Calculated output

Calculated Moon state

2026-09-10T12:03+00:00[UTC] · UTC

Schematic Moon phase: waning, 0.52% illuminated at a phase angle of 351.76 degrees. This represents illuminated fraction only, not sky orientation or observer hemisphere.
Schematic illumination only — not sky orientation or observer hemisphere.

Phase at the selected instant

New Moon

waning

0.52% illuminated

Lunar age
28.768 days
Phase angle
351.7633°
Selected instant
2026-09-10T12:03+00:00[UTC]
UTC instant
2026-09-10T12:03:00.000Z

Angle key

Read the cycle, not just the label

Phase angle follows the Moon through one continuous geocentric cycle. The familiar names sit at four measured landmarks rather than replacing the exact angle.

  1. 0°New Moon
  2. 90°First quarter
  3. 180°Full Moon
  4. 270°Last quarter

Lunar age

Elapsed UTC time since the strictly preceding calculated new Moon, not time since a local moonrise.

Event instants

A time-zone change alters the local display of an event, not the physical instant. Ambiguous clock-change inputs are rejected.