Soluna: Moon Calendar

Every tradition that kept a calendar kept it by the sky: a day begins at sunrise, a month begins at the new moon, a year turns at a solstice. Sacred Calendar computes all of it for wherever you are - no lookups, no network, everything from first principles on the device.

THE SUN, TODAY
Sunrise, solar noon, sunset and the exact length of the day, plus all three twilights: civil, nautical and astronomical dawn and dusk. The times come from Meeus's astronomical algorithms and are checked against NOAA's reference values.

THE MOON
The current phase drawn as it actually looks tonight, with illumination as a percentage, its age in days to two decimals, its position in the cycle, and whether it is waxing or waning. Then the two dates people plan around: the next new moon and the next full moon, to the minute in your time zone.

THE 24 SOLAR TERMS
The jieqi of the East Asian agricultural year - the moments the Sun's longitude crosses each multiple of 15°, from the winter solstice at 270° around to the next. Each term is shown with its Chinese character, and you can page through any year. The Today screen always names the next one and counts down to it.

FOUR CALENDARS, ONE DATE
Convert freely between Gregorian, the Julian Day Number, the Islamic (Hijri), the Hebrew and the Chinese calendars. Step a day at a time, or jump to today.

Each calendar is shown in its own script, not just transliterated: the Hijri date in Arabic with Arabic-Indic numerals, the Hebrew date in Hebrew numerals written the way they are actually written - including ט״ו and ט״ז for 15 and 16, which avoid spelling the divine name - and the Chinese date with its own day counting, 初一 through 廿三. In a Hebrew leap year the twelfth month is correctly named Adar I. No fonts are bundled; Android already has these scripts.

SIDEREAL TIME
Local and Greenwich sidereal time as a clock reading, the right ascension currently on the meridian, and the running Julian Day - the numbers you need if you are setting a telescope or casting a chart.

YOUR PLACE, NO PERMISSION
Search a built-in list of roughly 730 cities or type coordinates directly, and save as many places as you like. This app asks for no location permission at all - it never reads your device's position.

HOME-SCREEN WIDGET
Tonight's Moon, with your sunrise and sunset, refreshed at midnight.

WORKS OFFLINE, ALWAYS
Every number here is calculated, not fetched. Sun position, lunar phase, solar terms and every calendar conversion run on the device, so the app works identically in a basement or on a mountain. No account, no sign-in, nothing uploaded.

Free, supported by ads. A single one-time purchase removes every ad permanently, on any device signed in with the same Google account.