[LEAPSECS] Look before you don't leap

Rob Seaman seaman at noao.edu
Thu May 21 00:14:42 EDT 2015

On May 20, 2015, at 11:27 AM, G Ashton <ashtongj at comcast.net> wrote:

> I think calendars count observed day/night cycles.

They are not arbitrary day/night cycles.  What has been observed is Earth has a sidereal rotation period; during its annual lap around the Sun one of those rotations is unwrapped.  Hence the solar day.  

> Different cultures observe the transition from one day to the next at different points in the day, and change the transition point at various times without necessarily changing to a different calendar. Some cultures simultaneously observe different transition points for different purposes.

Recommend Kevin Birth’s work on time and culture, for instance see:


> Mean solar time, of course, has nothing to do with daylight saving time.

Tell it to the folks who think they can hide the Sun in the cracks between the timezones.


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