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WikiProject Time (Rated C-class, Top-importance)
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Do calendars really measure time?[edit]

I think a lot of misconceptions about calendars arise from the idea that a calendar measures time, like a clock or like a ruler measures distance.

All known calendars work by naming days (This is the definition in the Nupedia article). As such, a calendar can not measure time more accurately than 1 day. Furthermore, the duration of the day is known to vary in time owing to change in Earth's rotation rate, so is not a good standard in time measurement.

A solar calendar may measure years, by virtue of the fact that its year runs close to the cycle of seasons, but more accurate measurement can be got from an ephemeris.

The year even when measured in SI seconds, varies in duration and so can not be considered a unit of the same time that measured by SI seconds.

That's not a misconception at all--a calendar does indeed measure time just like a

clock does, just not very precisely. That doesn't mean it's not a measurement. A measurement simply answers the question "how much"; one can answer precisely or vaguely. If you ask "How much sand in this bucket?", One can measure in "handfuls" just as easily as kilograms, and one is performing essentially the same function. Likewise, "How much time since I was born?" can be answered roughly in years with the help of a calendar, and in fact is a much more useful measurement for most purposes than an exact measurement in seconds: I'm over 1.2 billion seconds old; quick-- can I go into a bar? Run for president? --Lee Daniel Crocker

--- Mr. Crocker is confusing entities (e.g. length) with units (e.g. meter), organizational nomenclature (e.g. kilo-meter), and measuring devices (ruler, laser interferometer). A calendar itself, whether the paper thing on the wall or the rules and conventions used to make them, is NOT an instrument or system of time MEASUREMENT. Chalking up a mark each day is sufficiently similar to a clock (counting regular events) to call that a time measuring device: but that is a simple day count and not a calendar. A calendar is a convention on organizing time, dividing it, or tracking it if you like; but NOT "measuring" it. You might as well call the "minute" a system of time measurement, or a clock, or a calendar: and it is neither of these. So I propose as the initial definition for the article:

"A calendar is a system for organizing periods of time. Calendars generally use the day as the fundamental unit, and give a label (names or numbers) to each day. Days are organized into larger units which usually are repeated in cycles, often based on some natural cycle like month or year. These properties facilitate recording events or periods of history and planning future events."

       -- 20011221: Tom Peters

For more discussion on Calendars and Time measurement, you may join the E-mail list CALNDR-L at

Some reformatting needed?[edit]

and additions, especially where it just links to a main article. Lockeownzj00 06:25, 13 Feb 2005 (UTC)

If you're thinking of placing main article links within the headings, then don't. That is to be avoided according to the Wikipedia:Manual of Style (headings). — Joe Kress 19:01, Feb 13, 2005 (UTC)

"new" calendars[edit]

Should we say something about the phenomenon of people trying to build new calendars (such as ) ? Is there a name for this, perhaps something like constructed calendar, analogous to constructed language ?

Some proposed calendars are at calendar reform. — Joe Kress 05:10, 2 Jun 2005 (UTC)

Moved from main article, by User:[edit]

I would like an article titled AD and/or ADE and BCE if BCE exists.

The article would explain the difference between AD and ADE when placed after the number of a year. For example 2006 AD and 2006 ADE. What does the E stand for and when should or can it be used? Thanks, Marvin L Morrison

hello wikipedians[edit]

I have to say .... I wold liked to see a quick referents table on when each calender was known to have bin calculated and taken in to use and so on. just saying it would be easier to visualize the time frame and also easier to remember :) thank you

Other Date Systems[edit]

Can a simple table be added to this article that describes different calendar systems in present and past use? It would be interesting to see at least a link to different types of calendar, and an explanation of their features (luni-solar, region first adopted, etc.) That way it would at least link to more detailed explanations. I was wondering about fixed 'switchover' dates in various calendars and the typology they use because I want to know about the reign of Urukagina in Sumer and how accurately his reign can be estimated. — Preceding unsigned comment added by (talkcontribs) 05:41, 17 May 2014 UTC

Systemic bias towards Eurasian calendars[edit]

It looks to me like this page, History of calendars, and List of calendars disproportionately cover calendars developed in Eurasia and the Near East. For example, the section Calendar § History mainly discusses calendars invented in Eurasia, as well as the Egyptian calendar. History of calendars has a decently sized section on Mesoamerican calendars but barely discusses African calendars. It's important for these pages to cover a representative sample of the world's calendars, especially Calendar and History of calendars, which are vital articles. Qzekrom (she/her • talk) 06:51, 24 September 2022 (UTC)Reply[reply]