[PYTHON DB-SIG] [comp.lang.python] Date-Time requirements (esp. for databases)
W. Craig Trader
Tue, 29 Oct 1996 22:23:06 -0500 (EST)
On Wed, 30 Oct 1996, Anthony Baxter wrote:
> Other methods the DateTime objects should have:
> strftime - takes a format string, returns the date as a string in the
> specified format. ("%Y%M%D %H:%M:%S" -> "19961029 11:57:00")
This is good, though it duplicates the existing `time' modules function.
> arithmetic - difference between two dates. adding dates - it should be
> possible to produce a DateTime object representing "1 week"
> and say DateTime(now) + DateTime("1 week").
I think you're wrong here - there should be multiple types: DateTime, as
already discussed, and Interval, which would represent a signed quantity
of a generic unit (ie: 10 minutes or 2 hours or 1 week or 5 years), or
possibly a combination. Math would look like this:
Interval + Interval => Interval
Interval - Interval => Inverval
DateTime + Interval => DateTime
DateTime - Interval => DateTime
DateTime - DateTime => Interval
Since we're talking about databases, the types should try to stick fairly
close to SQL, and SQL/92 already has provisions for DateTimes and
> Timezones. If the OS supports timezones, it should use it. Yes, this incurs
> some portability hassles, but that's the way things are - under Unix, the
> timezone support is very good, and should be used. If Windows or whatever
> has inadequate support for timezones, then something else should be provided
> for that.
Again, I'd want to look towards SQL for this type of problem - the
theory's probably already been solved - why work hard only to produce
something that isn't compatible with major databases?
> Hardcoding timezones is something that should be avoided. Particularly with
> daylight savings, which is a hideous political issue. Australia has 8 states
> and territories - nearly every one of these has different timezone/DST rules.
Well, at least South Australia is no longer 1.5 hours off from Queensland.
That was a *real* lousy system. Of course, Indiana in the States is the
worst - it varies county by county. <sigh>
- Craig -
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