[LRUG] Finding the duration between two DateTimes

[Piers Cawley]

On 30/05/07, Eleanor <eleanor at goth-chic.org> wrote:
> On 29 May 2007, at 13:33, Piers Cawley wrote:
> > On 28/05/07, Eleanor <eleanor at goth-chic.org> wrote:
> >> Then where you currently create your duration you could write:
> >>
> >>         duration = Duration.new(Task.duration)
> >>
> >> However from the perspective of a Task object you may not need any of
> >> this complexity. Just because something can be made into an object
> >> doesn't necessarily mean that it should...
> >
> > However, in the case of calendrical calculations, reifying a duration
> > makes a great deal of sense. Representing a duration internally as a
> > number of seconds makes a great deal less sense though. Consider the
> > problems inherent in 1.month, daylight savings, leap years, leap
> > seconds and the whole jujuflop situation that is timezones.
>
> It's true that anything to do with calendrical calculations is
> usually a nightmare, but doubly so in project management where
> there's a fair chance that two different calendrical systems will be
> in use: a gregorian calendar with all of its attendant
> inconsistencies, and a standardised man-month calendar. Reconciling
> these can be a real pain. All-told human schemes for marking time are
> amongst the more slippery concepts for computers to deal with. I
> think in Tim's case I'd use minutes as my standard unit if the
> purpose is basic time-management and only adopt a Duration class in
> the event that I wanted to write a feature-complete project
> management tool - but then again, I'm a lazy hacker so HMMV :)

Heh. Of course, if someone would just port the Perl DateTime library
to Ruby, life would be so much easier.