Calendar/talk

DO CALENDARS REALLY MEASURE TIME?

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.

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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

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