Re: [LEAPSECS] BBC - Leap second talks are postponed

From: Rob Seaman <>
Date: Thu, 17 Nov 2005 11:34:44 -0700

On Nov 17, 2005, at 2:45 AM, Clive D.W. Feather wrote:

> Microsoft *spit* Outlook calendar management talks about "GMT
> Daylight Savings Time" or some such idiocy. Every spring I respond
> to the first appointment request from my boss with "so do you want
> to meet at 10:00 GMT or 10:00 BST?".

Isn't this a reflection of Britain having a single time zone? The
four timezones of the contiguous U.S. produce a a very diverse set of
local time conventions. About one fourth of the states are split by
timezones. Indiana and Arizona have idiosyncratic daylight saving
rules (see, three
nested political entities with different DST rules). Certainly there
is occasional confusion about meeting times and TV schedules, but
this is a fact of synchronizing schedules across a wide extent of
longitude. In particular, the multiple timezones enforce a common
usage for daylight saving terminology. We have Eastern Standard Time
and Eastern Daylight Time, and similar pairs for the other
timezones: EST/EDT, CST/CDT, MST/MDT, PST/PDT. Which is to say that
daylight saving is properly viewed as a modification of the
underlying standard timezone system.

Contrarily, in Britain you have chosen to call your civil standard
time "Greenwich Mean Time" and your civil daylight saving time
"British Summer Time", rather than (for instance) British Standard
Time and British Daylight Time. It also happens that "Greenwich Mean
Time" has a technical definition as a deprecated international
standard. Other localities don't have this problem since nobody
(except under obscure circumstances) references "New York Mean Time",
but rather something like "Local Mean Time in New York". Greenwich
is an identifier associated with a locality. British is an
identifier associated with an extended territory, i.e., a timezone.

Perhaps folks can comment on international usage broader than my
parochial fixation on the United States?

Rob Seaman
National Optical Astronomy Observatory
Tucson, Arizona
Received on Thu Nov 17 2005 - 10:35:41 PST

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