[tz] The Mysterious Cube
sla at ucolick.org
Sun Nov 30 15:20:37 UTC 2014
On Sun 2014-11-30T10:32:45 +0000, Lester Caine hath writ:
> Interesting just scanning the differences between MSF and WWVB in
> relation to DST and leapseconds, but how does WWVB handle the different
> time zones in the US? And are they using TZ to determine when :)
The details of the WWV,WWVH,WWVH broadcasts have been tweaked many
times. Much of the history is detailed in the NBS/NIST publications.
Many of the tweaks were recorded and published as part of a CDROM
entitled "At the Tone", and this includes the exact moment of a number
of changes not easily found in NBS/NIST publications.
At the inception of WWVB in 1965 all the stations gave UT in Morse
code. WWVB was broadcasting purely atomic seconds with no attempt to
match the coordination with UT2 that was specified by CCIR Rec. 374.
WWV was located in Maryland and the voice announcements gave Eastern
Standard Time. WWVH voice announcements gave Hawaii Standard Time.
The CCIR issued Rec 374-1 in 1966, and that allowed for the Stepped
Atomic Time of WWVB as an experimental option.
At 1966-12-01T00:00:00 the Maryland transmitter stopped and the new
Fort Collins Colorado transmitter began. The voice announcments
became Mountain Standard Time. Earlier that year, however, the
Uniform Time Act had modified 15USC261 to modify the law such that
all of the US would use the same rules for daylight time starting
on 1967-04-30. Avoiding that issue, at 1967-04-28T21:00 WWV and
WWVH changed their voice announcements to be GMT. The voice kept
saying GMT even after the leap seconds of 1972, and finally
changed to saying Coordinated Universal Time on 1974-01-01T00:00.
Around the US the radio-controlled clocks that use WWVB to reset
themselves have switches on the back that allow the user to choose
which civil time zone is desired. The ones that work well also
detect the daylight time bits in the WWVB modulation, so when the
radio propagation is good they do the one hour reset.
Steve Allen <sla at ucolick.org> WGS-84 (GPS)
UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855
1156 High Street Voice: +1 831 459 3046 Lng -122.06015
Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
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