Thirteen moons. 369 days. Moon keeps the calendar and marks every moment. The light runs your day. Open to every system.
Our calendar was decreed in 1582. Our time zones were drawn for railroads. The world now runs on networks that never sleep. It deserves a clock built for all of us at once.
Thirteen equal moons replace twelve uneven months. Every year has the same shape.
A fixed 369-day year. Each moon is 28.38 Moon days, exactly one lunar cycle. No leap rules.
One mark for every moment, the same everywhere on Earth. Your day runs on local Sun time.
Years count from 0 AD, so arithmetic on dates finally works the way you expect.
Moon keeps the date. The light runs your day. Every moment gets a Moonmark.
The world runs on {{zoneCount}} different local clocks right now. Moon replaces all of them with one date, one Moonmark, and the light where you stand. Every beacon below is live.
The Gregorian year is twelve months of 28, 29, 30 and 31 days. Moon makes every moon one real lunar cycle, new moon to new moon, and thirteen of them make one year. Days stay whole: eight moons run 28 days and five run 29.
| GREGORIAN + TIME ZONES | MOON | |
|---|---|---|
| The second | 1 SI second | 1.0403730 SI seconds |
| Divisions | 12 months, 28 to 31 days, unrelated to the moon | 13 moons, each one real lunar cycle |
| Year length | 365 or 366, leap rules | 369, always |
| Clock | Dozens of local zones | One global time |
| Daylight saving | Shifts twice a year, region by region | Never |
| Year count | Starts at 1, no year zero | Starts at year 0 |
| Governance | Papal decree, 1582 | Open standard, open API |
Moon is open source. No signup, no key: any device, app or system can ask for the time and get one answer the whole planet agrees on. No zone tables. No DST patches.
READ THE DOCS{{apiJson}}
The math behind the standard. Every number here is reproducible from the spec.
The calendar. Moon is one count running underneath everything, read as the year, the 13 moons and the day, locked to the real moon. Every moment on it is a Moonmark. Your day runs on the light: Light counts up from first light, Dark counts up from sunset.
One exact moment on the Moon engine, the same for everyone on Earth, like 1928.05.03 09:12:04.205379905. Use it for launches, records, logs and proof of when something happened. Every Moonmark has its own link, so it fits in a QR code.
How you live the day on Moon. At first light, when the sun clears the horizon, the Light counter starts at 00:00:00 and counts up until sunset. Then Dark starts at 00:00:00 and counts up until the next first light, which begins the next Moon day. A meeting at Light 06:45 always lands at the same point in the daylight. In winter there is less Light, so Light 12:00 doesn't exist. Where the sun doesn't rise or set for weeks, the day starts at solar midnight.
It has, in pieces. Japan used daylight and night hours until 1873. Italy counted hours from sunset into the 1800s, and Babylonian hours counted from sunrise. They faded because clocks couldn't follow a moving sunrise and railroads needed one shared clock. Today every phone knows the exact sunrise where you stand, and the Moonmark gives everyone one shared moment. We didn't invent living by the light. We made it work again.
1 Moon second = 1.0403730490 SI seconds. It is derived, not chosen: 13 mean lunar cycles (13 × 29.530588853 days) divided into exactly 369 days of 86,400 Moon seconds. A Moon minute is 62.42 s, a Moon hour 1 h 2 min 25 s, and a Moon day 24 h 58 min 8 s in standard time.
The moon has two natural months. The sidereal month, one orbit measured against the stars, is 27.321661 days. The synodic month, new moon to new moon, is 29.530589 days. Their harmonic mean, the correct way to average two rates, is 2ab ÷ (a + b) = 28.3832 days, and 13 × 28.3832 = 368.98 days. Moon makes that a whole 369, so each moon is 28.3846 Moon days, within 2 minutes of the astronomical value. The Moon second is then sized so those 369 days span exactly 13 real lunations.
Tesla was famously drawn to the number three. Biographers describe him circling a block three times before entering a building and preferring hotel rooms with numbers divisible by three. The widely shared quote about the "magnificence of 3, 6 and 9" has no known source in his writings or interviews, so we do not attribute it to him. Moon's 369 comes from the moon's orbit, not numerology. The echo of Tesla is a fitting coincidence.
Yes. Each moon is the mean synodic month, the average time from new moon to new moon, and the count starts on a mean new moon. Individual new moons arrive up to about 14 hours early or late because the lunar orbit is elliptical, but that offset swings back and forth and never accumulates.
Year 0, Moon 1, Day 1, 00:00:00 is the first mean new moon of 0 AD: 23 January 0000 at 02:44 UTC. It is counted back exactly 24,736 lunations from the astronomical reference new moon of 6 January 2000, 18:14 UTC. Today is Year {{y}}.
Your phone shows the old clock, set by time zones and daylight saving. Moon doesn't use it. A Moon day is about 58 minutes longer than one turn of the Earth, so Moon never tries to tell you the hour. The light does that, and the Moonmark is the exact moment underneath.
A Moon year is 383.9 standard days, about 18.7 days longer than the solar year, so the seasons move steadily through the Moon calendar and return to the same moons roughly every 19.6 years. Sun tracks them for you: your season, sunrise and sunset, and every equinox and solstice as a Moonmark.
Each day belongs to the moon it starts in. That gives eight moons of 28 days and five of 29 (moons 1, 3, 6, 8 and 11), totaling 369. The pattern is identical every year.
Nowhere you need them. To meet someone anywhere, share a Moonmark: one moment, the same for everyone. To know if they are up, look at their light, like Tokyo at Light 00:45. Sunrise and sunset only depend on where you stand, so Light and Dark need a location, never a time zone.
Moon is defined from the SI second, which is set by cesium atomic clocks, and computed from Unix time so every system gets the same answer. Moon seconds = (Unix ms − epoch ms) ÷ 1040.3730490. The epoch is −62,165,308,562,979 ms.
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