Calendopaedia - Figures

How long is a year? Is a lunar month 29 or 30 days? What is a second?

Here are the figures that I left out of other pages to stop it looking too complicated. For those of you who want to know the details - this is the place. To find out what the terms used here mean look for the relevant page on the Site Index page.

How long is a year? A tropical year is 365.242199 days UT which is equal to
365 days, 5 hours, 48 minutes and 45 seconds.
A sidereal year is 365.256366 days UT which is equal to
365 days, 6 hours, 9 minutes, and 9.5 seconds.
An anomalistic year is 365.259636 days UT which is equal to
365 days, 6 hours, 13 minutes, and 33 seconds.
How far has the Gregorian calendar
drifted since it was decreed in 1582?
2 hours, 59 minutes, 12 seconds.
When will the Gregorian calendar be one whole day out? The year 4909 AD.
How many lunar months are there in a year? 12.368267
How long is a lunar month? Its average length is 29 days, 12 hours, 44 minutes, and 2.9 seconds, or 29.530589 days.
How long is a second? The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Well you wanted to know!

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