[LEAPSECS] Definition of Standard time - Brooks Harris

Rob Seaman seaman at noao.edu
Sun Feb 16 18:14:55 EST 2014

On Feb 16, 2014, at 3:05 PM, Clive D.W. Feather <clive at davros.org> wrote:

> Brooks Harris said:


>> "Where daylight saving time is used, the term standard time typically

>> refers to the time without the offset for daylight saving time.".


>> That is consistent with my understanding of "Standard time".


> But not mine.


> "standard time" is to be contrasted with "local time". Both GMT and BST are

> "standard time" in the UK.


My personal experience of what is typical usage in the U.S. and Chile would be the opposite. "Local" time almost universally means what the clock says right now (or said at the time in question).

On the other hand, calling something standard time (e.g., "Pacific Standard Time") never means daylight saving time, rather that is "Pacific Daylight Time"). Contrast EST, CST, MST and PST with EDT, CDT, MDT and PDT. Since Arizona (outside Navajo lands) never observes MDT, this is something we're sensitive to from having to shift schedules twice a year relative to everybody else in the country.

The observatory also has telescopes and personnel in Chile, and the anti-correlated seasonal daylight saving time shifts from CLT to CLST are referred to similarly. (I'd welcome correction regarding differences in Spanish usage.) In the U.S. I've lived in MA, PA, WY and HI (which also doesn't observe DST) and usage was similar to what I describe: local time means what the clock says and standard time refers to the opposite of daylight saving time.

It would be interesting to explore the usage in other locations and by various communities. And of course, only a minority of the world's population observe DST at any time of the year, so it might be moot to distinguish the two in places that don't.

Anybody from Canada want to report on usage? There's a large overlap in timezones with the U.S., but as a member of the Commonwealth you might be expected to have usage derived from the U.K.


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