RE: Timezones in get-hours-from-dateTime etc.

> 
> Here is a suggestion for a supplemental convenience feature 
> that will hopefully make everybody happy:

Adding more functions and parameters in the language makes everybody happy
except those who want the language to be smaller - which is nearly
everybody!

I would rather try to identify a minimal set of primitive functions that can
be composed to do everything you need to do, rather than have lots of
convenience features that bloat the language.

Michael Kay


> 
> get-XXX-from-dateTime accepts an optional second argument 'timezone'
>     such that
> 
> 	get-hours-from-dateTime($dt, $tz)
> 
>     is equivalent to:
> 
> 	get-hours-from-dateTime(adjust-dateTime-to-timezone($dt, $tz))
> 
> This way the following expression returns the normalized UTC 
> component:
> 
> 	get-hours-from-dateTime($dt, 0)
> 
>       (Note: using the duration notation proposed by Michael Kay)
> 
> while the following expression returns the component as 
> specified initially (i.e. using the timezone that was 
> specified or implicit when
>    the date/time object $dt was created):
> 
> 	get-hours-from-dateTime($dt)
> 
> to get the component in the implicit timezone:
> (not necessarily the same as above)
> 
> 	get-hours-from-dateTime($dt, implicit-timezone())
> 
> 
> 
> -- 
> Xavier FRANC
> >  
> > 
> http://lists.w3.org/Archives/Public/public-qt-comments/2003Sep/0124.ht
> > ml
> > 
> > suggested that the date/time component extraction functions (for 
> > example,
> > get-hours-from-dateTime()) should return components of the 
> localized time,
> > rather than the normalized time.
> > 
> > (Terminology: localized time = the time in the timezone 
> represented by 
> > the timezone component of the value; normalized time = the same 
> > instant of time represented in timezone UTC)
> > 
> > On reflection, I'm inclined to agree with Xavier: I think 
> we have got 
> > this wrong. The date/time is presented in localized form when 
> > converting it to a string, and when using the XSLT 
> format-dateTime() 
> > family of functions. I think it will be less confusing if we 
> > consistently present date/time values in the localized form, and 
> > require users to use adjust-X-to-timezone if they want something 
> > different.
> > 
> > Currently, if you want the components of the localized 
> value, you have 
> > to call adjust-dateTime-to-timezone() with () as the second 
> argument, 
> > and then call get-hours-from-dateTime.
> > 
> > With this change, a user who wanted components of the 
> normalized value 
> > would use adjust-dateTime-to-timezone() to adjust the 
> timezone to UTC, 
> > and then extract the component values.
> > 
> > Specifically (in XQuery syntax):
> > 
> > let $utc := xdt:dayTimeDuration("PT0H"),
> >     $ndt := adjust-dateTime-to-timezone($in, $utc) return
> >     get-hours-from-dateTime($ndt)
> > 
> > We might also want to consider changing the default for the second 
> > argument of adjust-X-to-timezone() so it adjusts to UTC, since 
> > adjusting to the local timezone can easily be achieved by supplying 
> > implicit-timezone() as the second parameter. Alternatively, if my 
> > proposal on durations is accepted, then 
> > adjust-dateTime-to-timezone($in, 0) will return the 
> normalized value.
> > 
> 
>