Light Calendar 2025/26

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The year 2025/26 runs from 03.02.2025 to 02.02.2026 and has the following astro­nomical fixed points: 17th New March (VE), 17th New June (SS), 16th New Septe (AE), 16th New Dece (WS) – explanation below, V1.2.19

< 2024/25 | 2025/26 | 2026/27 >

< 2024/25 | 2025/26 | 2026/27 >

Explanation:
The Light Calendar arranges the solar year into four 90° sections of apparent ecliptic solar longitude. The main transitions are at 315°, 45°, 135° and 225°. The equinoxes and solstices (0°, 90°, 180°, 270°) lie at the centres of these sections in solar longitude. This creates 4 seasons with distinct character: Early Spring (days rapidly get brighter each day/ΝFeb-ΝApr, warmth arrives delayed), Early Summer (time of long days/ΝMay-ΝJul), Early Autumn (days rapidly get shorter each day/ΝAug-ΝOct), Early Winter (dark season with little daylight change/ΝNov-ΝJan).

The astronomical transitions are instants; the calendar maps them to whole UTC days. The Light Year begins with the UTC civil day containing the 315° crossing. With the month pattern 29–31–31 | 31–32–31 | 31–31–30 | 29–30–29/30, the 45°, 135° and 225° transitions fall on the last or 1st day of the neighbouring months, while equinoxes and solstices fall on the 16th or 17th day of the middle month. The additional leap day is currently placed at the end of New Jan (marked ¹). For practical reasons the year number still changes on 1st Jan as usual.

The lunations of a light year are numbered 1-13 (similar to week numbers). A lunation belongs to the light year containing its full-moon night. Sections at the year boundary without a full moon are labelled Π; moon-night numbering continues. A lunar month ends with the new moon. New and full moons are assigned by local time: before 12:00 they belong to the preceding night, from 12:00 onwards to the same day's night. The day after new moon is moon night 1; the next new moon is moon night 29 or 30 and the final night of the cycle.

This PHP version uses astronomical approximation formulae and does not reach the full precision of the app. The Light Year boundary and Light phases are calculated from apparent ecliptic solar longitude. All times shown in Central European Time (CET/CEST).

Lunations of light year 2025/26:
1st Moon – 03.02.25 … full: 12.02.25 … new: 27.02.25
2nd Moon – 28.02.25 … full: 13.03.25 … new: 28.03.25
3rd Moon – 29.03.25 … full: 12.04.25 … new: 27.04.25
4th Moon – 28.04.25 … full: 12.05.25 … new: 26.05.25
5th Moon – 27.05.25 … full: 10.06.25 … new: 25.06.25
6th Moon – 26.06.25 … full: 10.07.25 … new: 24.07.25
7th Moon – 25.07.25 … full: 08.08.25 … new: 22.08.25
8th Moon – 23.08.25 … full: 07.09.25 … new: 21.09.25
9th Moon – 22.09.25 … full: 06.10.25 … new: 21.10.25
10th Moon – 22.10.25 … full: 05.11.25 … new: 19.11.25
11th Moon – 20.11.25 … full: 04.12.25 … new: 19.12.25
12th Moon – 20.12.25 … full: 02.01.26 … new: 18.01.26
13th Moon – 19.01.26 … full: 01.02.26

The moon display (see above) works as follows: Μx·y (p/z) = x. Moon, y. moon night, p=full-moon night, z=new-moon night; Π·y (p/z) = year-boundary section without a full moon.

In the same vein is 'Gordon's Sun Clock', a single-hand clock whose dial changes daily with the seasons. It is available as a free Android app:

Gordon’s Sun Clock >
Info about Light Calendar (Github) >

For more precise calculations, please check the Android app or the web app.