Re: Julian Date and Leap Seconds


Greg Neill wrote:
UTC, being tied to the actual rotation of the Earth, is not a
strictly uniform time scale so it's bound to drift away from
time scales that are uniform unless periodic corrections are
made.

Just to be clear, UTC is a uniform time scale except for the leap
seconds (and perhaps some relativistic corrections). There are other
time scales that are non-uniform at the sub-second level. See the FAQ
C.02 at http://sciastro.astronomy.net/sci.astro.3.FAQ

Julian day number is based upon a uniform scale.

Are you sure about that?

http://tycho.usno.navy.mil/systime.html

This reference says "Julian Day Number is a count of days elapsed
since Greenwich mean noon on 1 January 4713 B.C., Julian proleptic
calendar. The Julian Date is the Julian day number followed by the
fraction of the day elapsed since the preceding noon." That suggests
to me that it is based on UT2 and is therefore non-uniform.

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