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.
Calculated Moon state
- Phase
- Waxing Gibbous
- Illuminated fraction
- 82.20%
- Lunar age
- 10.011 days
- Direction
- waxing
- Nearest principal event
- First Quarter, previous, 3 days, 9 hours, 24 minutes away
- Phase angle
- 129.9749°
- Selected instant in Europe/London
- 2028-08-30T12:00+01:00[Europe/London]
- UTC instant
- 2028-08-30T11:00:00.000Z
Show every previous and next principal phase
| Event | Previous in Europe/London | Previous UTC | Next in Europe/London | Next UTC |
|---|---|---|---|---|
| New Moon | Sunday, 20 August 2028 at 11:44:18 BST | 2028-08-20T10:44:18.950Z | Monday, 18 September 2028 at 19:24:12 BST | 2028-09-18T18:24:12.490Z |
| First Quarter | Sunday, 27 August 2028 at 02:36:27 BST | 2028-08-27T01:36:27.888Z | Monday, 25 September 2028 at 14:10:39 BST | 2028-09-25T13:10:39.556Z |
| Full Moon | Saturday, 5 August 2028 at 09:10:25 BST | 2028-08-05T08:10:25.424Z | Monday, 4 September 2028 at 00:48:12 BST | 2028-09-03T23:48:12.853Z |
| Last Quarter | Sunday, 13 August 2028 at 12:45:53 BST | 2028-08-13T11:45:53.686Z | Tuesday, 12 September 2028 at 01:46:19 BST | 2028-09-12T00:46:19.895Z |
How to read the result
Phase angle is the Moon's geocentric ecliptic longitude relative to the Sun: 0° is new Moon, 90° first quarter, 180° full Moon, and 270° last quarter. Lunar age is the elapsed UTC time since the strictly preceding calculated new Moon; it is not the time since an observed local moonrise.
Principal event times are instants and therefore do not change when the display time zone changes. Only their local representation changes.
Scope and limitations
- Supported local years: 1900–2100.
- Ambiguous or nonexistent local times at clock changes are rejected.
- Moonrise, moonset, horizon visibility, weather, and location-based observation are outside this calculation.
- Displayed values are rounded; the calculation retains greater precision internally.
See the phase calculation methods and astronomical sources. For the same exact instant, calculate Moon distance and apparent size, or add an observer location in the Moon Position Calculator. The Lunar Eclipse Finder searches global events before and after a selected time.