[LEAPSECS] An example

michael.deckers michael.deckers at yahoo.com
Wed Nov 3 06:00:45 EDT 2010

On 2010-11-02 22:57, Poul-Henning Kamp wrote:

> In message<4CD07CD9.7080505 at yahoo.com>, Michael Deckers writes:

> > Isn't a day always exactly 86400 s, in whatever time scale you

> > are considering?

> No, because the second is defined using quantum mechanical properties

> of Cs133, not as being 1/86400 of whatever day you look at.


Right, but the question is how the time unit day is defined,
not the second. And the BIPM defines it as 86400 s, see

A mean solar day (that is, d(TAI)/d(UT) days or d(TT)/d(UT) days)
is a bad choice for a time unit (unless one specifies the date)
because it is changing over time. Even a "day of TAI" would be
a bad choice because the rate d(TT)/d(TAI) has changed over time.

Michael Deckers.

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