The same instant, in a calendar where every month is exactly four weeks.
- Month
- Weekday
- Moon
- Revolution
- Next season
One year, two ways to cut it
The same days, in both calendars. Nothing is added and nothing is removed: they are simply arranged differently.
Your real date
Put in your birthday, or any other date. The fixed calendar gives it another name, and a weekday that will never move again.
Thirteen identical months, one header row for all thirteen. The Gregorian calendar needs twelve different grids to say the same thing.
Where the Earth is pointing
The axis leans 23.44 degrees and does not move all year. What travels around it is the Sun. Speed time up and the mechanism of the seasons explains itself.
1.5 MB of NASA imagery, once
Drag the globe to move around it.
- Instant shown
- Sun overhead at
- Your meridian
- Where you are
Where we are on the orbit
A year is one lap. Here is how much of it is done, and the circle is to scale: the Earth's orbit is far less oval than it is usually drawn.
The Moon, which follows nobody
Twenty-eight days is not a lunation. That is the most honest caveat to make about a thirteen-month calendar, and it deserves to be shown rather than buried.
Thirteen constellations
The zodiac has twelve signs and the sky has thirteen constellations. The two have been drifting apart for two thousand years.
Three times that never line up
The calendar we use, the one we could use, and the Moon. On the same axis, for the same year.
Kodak lived sixty-one years on thirteen months
This calendar is not a forum curiosity. It ran for real, inside a company of a hundred thousand people, for longer than most of the software we use has existed.
- 1902
Moses Cotsworth publishes the plan
A statistician for the British railways, he spends years comparing months of different lengths and concludes that the problem is not the data but the calendar.
- 1923
The League of Nations takes it up
An international committee shortlists the fixed calendar out of one hundred and thirty reform proposals. It never reaches a vote.
- 1928
Kodak adopts it
George Eastman puts the thirteen months into use across his entire company. Payroll, accounting and production all move onto strictly equal periods.
- 1937
The last serious attempt fails
The opposition comes mostly from the churches: a day outside the week breaks a seven-day cycle that has run unbroken for millennia.
- 1989
Kodak stops
Sixty-one years on, the company returns to the Gregorian calendar. Not because the system worked badly, but because nobody else was using it.
So what about October?
October means eighth, November ninth, December tenth. Those names are fossils of a Roman calendar that began in March and had only ten months. January and February were added in front, and nobody ever renamed the end of the year.
That is a different story from the thirteen months, and the two are better kept apart: here, inserting Sol pushes October to eleventh place, not to eighth.
Why calendar reforms fail
None of them has ever failed on a technical problem. They fail on the week. The seven-day cycle has turned without interruption for thousands of years, through empires and revolutions, and a day outside the week breaks it.
The French Republican calendar lasted twelve years with its ten-day weeks. The Soviet five-day calendar lasted eleven. The Gregorian one is not better: it is simply already there, in every contract and every system in the world. It is a standard, not a choice.
So is there a truly fixed way to measure time?
Yes. But it is not a calendar, and that is exactly why it works.
A calendar has to reconcile three periods: the Earth's rotation, the lunation, and the trip around the Sun. All three are set by independent physical mechanisms that know nothing about each other. No whole number of days makes a year, and no whole number of lunations makes one either. They are incommensurable in the strict sense: there is no common unit. Every calendar therefore lies about at least one of the three.
Worse: none of the three is constant. The day is getting longer by about 1.8 milliseconds a century, braked by the tides. The tropical year is shrinking by half a second a century. The tilt of the axis is slowly decreasing, and this site recomputes it for each instant rather than freezing it at 23.44°. The gap between clock time and the Earth's actual rotation even has a name, delta-T, and it has to be corrected for to date a full moon to the minute.
Fixed time does exist, and it was obtained by abandoning the sky altogether. Since 1967 the second has not been a fraction of a day but 9,192,631,770 oscillations of a caesium-133 atom. It no longer depends on the Earth. That is the only reason it does not drift.
Astronomers made the same choice three centuries earlier. The Julian Day, proposed by Joseph Scaliger in 1583, is a plain count of days running since 1 January 4713 BC. No months, no weeks, no leap years. A number that goes up. That counter, not the Gregorian calendar, is what every calculation on this site is anchored to.
The time right now, without a calendar
- Julian Day
- Unix time
- Caesium oscillations
- The day is lengthening
So here is the honest answer: fixed time is entirely possible, provided you give up on it being liveable. Nobody schedules a meeting for Julian Day 2461261. A counter is exact and unusable; a calendar is approximate and human. Cotsworth's thirteen months are the best known compromise between the two: they give up the Moon, keep the week, and pay for their regularity with two days that belong to nothing at all. That is an admission, not a flaw.
The same thing, on your home screen
A widget showing the fixed-calendar date, its Gregorian equivalent, and the phase of the Moon. Nothing else.
Tell me when it shipsAn email, not a form, not a database. The site still has no server and that is exactly right.
Everything computes on the device
This site's engine is plain TypeScript with no network. It runs just as well inside an offline widget.
The date keeps its weekday
A fixed-calendar date holds its weekday for life, so a widget never has to work it out again.
The Moon in its true phase
The disc is drawn from the illuminated fraction, not approximated by two overlapping circles.
No account
There is nothing to store: a date is enough to derive everything. No reason to ask for anything.