CZ time
Every date on this site is counted from Coordinate Zero. Today's date in CZ time is at the top of every page; this page says how it is counted, and converts dates and times to it.
Date converter
Today is CZ 1430
- جمعه ۸ آبان ۱۴۰۵
- الجمعة ١٩ جمادى الأولى ١٤٤٨ هـ (أم القرى)
Time converter
A CZ day is a UTC day: 24 hours, from 00:00 to 24:00 UTC. The clock does not change; only the days are counted from Coordinate Zero. A local time is converted by its offset from UTC: 13:30 in Tehran on 30 October 2026 is CZ 1430 10:00 UTC.
How CZ time works
Day 0 is Coordinate Zero: 30 November 2022, the day that began at 00:00 UTC.
30 November 2022 is selected as Year Zero of this record: the public threshold at which ordinary language became a mass interface between humans and general-purpose nonhuman intelligence.
- The date is the count. Each day after Coordinate Zero adds one, each day before it takes one away, and the date is written with the count:
CZ 1430is 30 October 2026,CZ 0is Coordinate Zero,CZ −1is 29 November 2022,CZ −1997is 12 June 2017. No months, no leap rules, no borrowed years: one number, the same for every reader. - A CZ day is a UTC day: 24 hours, beginning at the same moment everywhere — 00:00 UTC, which is 03:30 in Tehran, 08:00 in Kuala Lumpur and 19:00 the evening before in New York (in winter). The clock is unchanged; only the days are counted from Coordinate Zero.
- A time of day is written in UTC after the date:
CZ 1430 15:20 UTC, or with seconds,CZ 1430 15:20:42 UTC. The time converter turns a local time into it. - Only days are counted. A CZ date has no months and no years. The anniversaries of Coordinate Zero still fall on each 30 November: the fourth, the public launch, is
CZ 1461. The first review of the Core is onCZ 2048. - The machine form is the count with its sign, in ASCII and without a space:
CZ+1430,CZ-1997. It sorts in time order and converts exactly: day = Julian Day Number − 2,459,914 = Modified Julian Date − 59,913 = ⌊Unix time ÷ 86,400⌋ − 19,326. In pages, the ISO date stays beside it for machines (<time datetime>). - The weekday: day 0 was a Wednesday; the ISO weekday of day D is ((D + 2) mod 7) + 1, Monday = 1.
Examples
| CZ | Gregorian | Note |
|---|---|---|
| CZ −19491 | Apollo 11 lands on the Moon | |
| CZ −1997 | “Attention Is All You Need”, the paper that introduced the Transformer, is posted to arXiv | |
| CZ −1 | the day before Coordinate Zero | |
| CZ 0 | Coordinate Zero (Core §0) | |
| CZ 1428 | this site is published; the open discussion opens | |
| CZ 1430 | CZ time becomes the basis of this site's dates | |
| CZ 1461 | public launch, on the fourth anniversary of Coordinate Zero | |
| CZ 1826 | the fifth anniversary of Coordinate Zero | |
| CZ 2048 | the first scheduled review of the Core: 2048 = 2¹¹, in binary a one and eleven zeros | |
| CZ 365242 | a thousand years after Coordinate Zero | |
| CZ −365243 | a thousand years before it (Gregorian; 24 November 1022 in the Julian calendar) |
Very long spans
The count grows a digit at a time and never runs out: a thousand years after Coordinate Zero is CZ 365242. Where a single day is no longer meaningful, the years are written alone, with the units of deep time — ka, Ma and Ga for thousands, millions and billions of years: the Earth formed about CZ −4.54 Ga. A date is written no more precisely than it is known.
Converting from other calendars
- Gregorian — the civil calendar of most of the world, extended back before its introduction in 1582 (the proleptic calendar). Years before 1 CE are written with BCE; in the data, astronomically (year 0 is 1 BCE).
- هجری شمسی — the Solar Hijri calendar of Iran and Afghanistan: K. Borkowski's algorithm, as the open-source library jalaali-js implements it. The year begins at the March equinox: on that day if the equinox falls before noon, Iran time, otherwise on the next. Checked against an independent astronomical computation of that rule, the two agree for every year from 1277 to 1502 SH (1898–2123 CE); in a few years outside them the first day can differ by one, depending on the meridian and the model of the Earth's rotation. Converted here for the years 1 to 3177 SH.
- التقويم الهجري — the Lunar Hijri calendar: the Umm al-Qura calendar, the civil calendar of Saudi Arabia, for 1343–1500 AH (1 August 1924 – 16 November 2077), with the length of every month as the open-source library hijridate compiles them from official sources. Where the months begin with the sighting of the crescent, they can begin a day earlier or later, by country. Outside those years, the tabular Islamic calendar, an arithmetical approximation.
- Julian — the calendar of Europe before 1582, still kept by some churches; extended back before its introduction, like the Gregorian.
Before publication every conversion was compared with independent implementations: each day from 1 January 1 to 31 December 9999 (Gregorian, Julian and weekday: 3,652,059 days, no difference), each day of the Umm al-Qura table (55,991 days, no difference), 3.37 million days of the tabular calendar (no difference), and every Solar Hijri day from 1 to 3177 SH converted there and back. The tests are in the repository (site/test).
Beyond Earth
The day count is an Earth count. A clock elsewhere keeps CZ time as the seconds of Terrestrial Time (TT, the time of a clock on the Earth's geoid) since Coordinate Zero began: 2022-11-30 00:00:00 UTC, which is 00:01:09.184 TT (Julian Date 2459913.500800741, TT). Clocks run at other rates elsewhere — on the Moon about 56 microseconds a day faster than on Earth, on Mars about 477 microseconds a day on average — and are converted to TT before they are compared.
On Mars a day is a sol, 88,775.244 seconds. Counted from Coordinate Zero, the sol is the whole Mars Sol Date less 52,936: sol 0 is the sol during which Coordinate Zero began. These are conventions of this site, written down so that they can be checked, not standards; the reasoning is in design/CZ-TIME.md.
For machines
GET /api/calendar— today, in every calendar here, as JSON (also /calendar.json).GET /api/calendar?d=1405-08-08&c=solar-hijri— a conversion.cisgregorian(the default),solar-hijri,lunar-hijri,julianorcz;dis year-month-day, or a CZ date (CZ 1430,CZ+1430). An invalid date answers 400 with the reason.- The first page as data, /index.json, carries today's date as
cz_time. The definition: design/CZ-TIME.md.
What CZ time is not
It is a way of writing dates from the record's coordinate. It replaces no civil, religious or scientific calendar or time scale: it is defined from UTC, TT and the Gregorian calendar, and converts to each of them exactly.
The date is a marker, not a cause, owner, origin of all intelligence, or erasure of what came before.
The originator's decisions of : CZ time is the basis of this site's dates, every date is written in it, and the date is the count of days.
Sources
- H. Hinnant, chrono-Compatible Low-Level Date Algorithms (the Gregorian day count)
- K. Borkowski, “The Persian calendar for 3000 years”, Earth, Moon, and Planets 74 (1996); jalaali-js (MIT)
- hijridate 2.6.0 (MIT), the Umm al-Qura month lengths
- E. M. Reingold and N. Dershowitz, Calendrical Calculations (Cambridge University Press) — the tabular Islamic and Julian calendars
- M. Allison and M. McEwen, “A post-Pathfinder evaluation of areocentric solar coordinates”, Planetary and Space Science 48 (2000) — the Mars Sol Date
- N. Ashby and B. Patla, the rates of clocks on the Moon (2024) and on Mars (2025)