[Pharo-project] What can be negative regarding timezones with date-related objects?

Sven Van Caekenberghe sven at beta9.be
Sat Jun 9 14:05:24 EDT 2012


Not used as offset in DateAndTime, Durations can be anything, both negative as well as positive, like in

'2010-01-02' asDate - '2012-06-08' asDate

'2010-01-02' asDate - DateAndTime now

On 09 Jun 2012, at 19:53, Mariano Martinez Peck wrote:

> 
> 
> On Sat, Jun 9, 2012 at 2:53 PM, Sven Van Caekenberghe <sven at beta9.be> wrote:
> 
> On 09 Jun 2012, at 14:24, Mariano Martinez Peck wrote:
> 
> > The seconds/nanoseconds are always positive when normalized.
> >
> > Are you sure?
> > I have just changed (for testing) to this:
> >
> >     DateAndTime localTimeZone: (TimeZone timeZones detect: [:tz | tz abbreviation = 'EST']).
> >
> > And now if I do:
> >
> > DateAndTime now offset asSeconds ---->   -18000
> 
> The seconds/nanoseconds in DateAndTime itself are like that,
> the TZ offset can be positive and negative:
> 
> http://en.wikipedia.org/wiki/Timezone
> 
> <<Most of the 40 time zones on land are offset from Coordinated Universal Time (UTC) by a whole number of hours (UTC−12 to UTC+14), but a few are offset by 30 or 45 minutes.>>
> 
> 
> 
> Ok, perfect. And what about durations outside DateAndTime. Say if I do: "-123 seconds"   is that valid?  I mean, should we accept normal durations (not the instVar offset of a DateAndTime) with negative seconds/nanoseconds?
> 
> thanks
> 
> 
> -- 
> Mariano
> http://marianopeck.wordpress.com
> 





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