[LEAPSECS] "old UTC" and "new UTC"

Rob Seaman seaman at noao.edu
Sun Mar 25 16:46:02 EDT 2012

On Mar 24, 2012, at 1:54 PM, Steve Allen wrote:

> There is also the interesting assertion that in the US the NBS was

> responsible for frequency and USNO was responsible for time.

No comment (or strong opinion) about the politics. Frequency and time are not, however, interchangeable concepts even if they are closely related. SI (through whatever national and international authorities) is founded on a frequency reference. See:


in which the keystone of the entire international system of units is a frequency standard:


Time, on the other hand, is a complex concept of diverse meanings. It will come as no surprise that I regard civil timekeeping as most closely allied with its meaning as an angular reference.

It could bring clarity to the discussion to clearly delineate frequency use cases from duration use cases. Whether both kinds of timepiece are managed by the same agency is a separate question.


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