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 http://iraf.noao.edu/~seaman/leap/3nations.pdf, 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
