Re: Time Bases and Timekeeping (was: Re: Valentins day :-)

Bill Gunshannon wrote:
In article <176uZD2KcidF-pn2-hQFs4FPdg62S@xxxxxxxxxxxxxxxx>,
"Bob Eager" <rde42@xxxxxxxxxxx> writes:
On Sun, 15 Feb 2009 12:29:32 UTC, Joseph Huber <joseph.huber@xxxxxxxxxxxxxx> wrote:

But ... my VMS time is local time here, even my Unix time!
UNIX systems usually store the time as UTC, and then adjust for the local time zone.

Since when? I have been doing Unix for 3 decades and have always used
local time. Most Unixes today give you the option and I do know people
who use GMT but I have never seen any advantage in doing it.

Unix and C have used UTC/GMT as the time base for eons, if not all the way back to the inception of the platform. (I've only started using Unix around 1983 or so, so I'm somewhat of a newbie.)

The display of UTC/GMT is common when servers don't have a good mechanism for displaying local time on a per-process basis, or when there's a specific reason to use UTC/GMT for all external operations; when the end-users are operating across time zones. It's also a common choice when you can't or won't update your timezone definitions and you're operating across zones and for whatever reason.

OpenVMS has never had a particularly good ability to display application-specific and per-process time zones.

Unix has had that.

Various OpenVMS boxes can and sometimes will choose to set native to and to display UTC/GMT to avoid having to deal with local time, with daylight saving time (DST) and/or with using and loading new timezone definitions.

Pendant notices: Yes, I know that UTC and GMT aren't quite the same time, and that time_t only approximates UTC, and that the approximation of UTC isn't quite the same as TAI, either.

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