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
- Selected local instant
- 2026-08-27T16:33+01:00[Europe/London]
- UTC instant
- 2026-08-27T15:33:00.000Z
- Phase
- Full Moon
- Phase angle
- 173.7539°
- Illuminated fraction
- 99.70%
- Lunar age
- 14.914 days
- Direction
- waxing
- Nearest principal event
- Full Moon, next, 0 days, 12 hours, 46 minutes away
Adjacent principal phases
| Event | Previous in Europe/London | Previous UTC | Next in Europe/London | Next UTC |
|---|---|---|---|---|
| New Moon | Wednesday, 12 August 2026 at 18:37:11 BST | 2026-08-12T17:37:11.343Z | Friday, 11 September 2026 at 04:27:28 BST | 2026-09-11T03:27:28.467Z |
| First Quarter | Thursday, 20 August 2026 at 03:46:58 BST | 2026-08-20T02:46:58.247Z | Friday, 18 September 2026 at 21:44:24 BST | 2026-09-18T20:44:24.674Z |
| Full Moon | Wednesday, 29 July 2026 at 15:36:19 BST | 2026-07-29T14:36:19.011Z | Friday, 28 August 2026 at 05:19:06 BST | 2026-08-28T04:19:06.085Z |
| Last Quarter | Thursday, 6 August 2026 at 03:21:58 BST | 2026-08-06T02:21:58.672Z | Friday, 4 September 2026 at 08:51:42 BST | 2026-09-04T07:51:42.224Z |
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 method and validation notes and astronomical sources.