How the Moon calendar works
Phase events are recorded as UTC instants and shown in the selected IANA time zone. The UK default is Europe/London, including its daylight-saving transitions.
Daily calendar values
Each daily row is sampled at 12:00 local time. Local noon is documented because a continuously changing phase has no single value for an entire civil day. Phase names come from eight 45-degree sections of the geocentric Moon–Sun ecliptic longitude cycle.
Principal phase events
New Moon, first quarter, full Moon and last quarter use calculated event instants rather than the daily noon sample. The event keeps its UTC instant, then receives a local date and time for the selected zone.
Illumination, lunar age and rounding
Illumination is the calculated fraction of the lunar disc lit from the observer's geocentric perspective. Lunar age is elapsed time since the previous calculated new Moon. Displayed percentages, angles and ages are rounded for readability.