Re: [pdf-devel] Re: Calendar spans

[Stuart Jansen]

On Sun, 2008-05-18 at 19:19 +0200, Aleksander Morgado wrote:
> > 
> >    The problem is that the result cannot be February 31st. So which
> >    would be the resulting epoch?
> > 
> > Using the precedence rule first we add 1 year to 2007-01-31 resulting
> > in 2008-01-31. Then we add 1 month (February in a leap year) resulting
> > in 2008-02-29.
> > 
> > What do you think?
> > 
> 
> Well... don't really like it. This means that there are three different 
> time origins for which the calendar time span gives the same result... 
> isn't it?
> 
> 29 January 2007 + (1 year + 1 month) = 29 February 2008
> 30 January 2007 + (1 year + 1 month) = 29 February 2008
> 31 January 2007 + (1 year + 1 month) = 29 February 2008

Have you considered doing a survey of other Date/Time/Calendar
implementations to find out how they solve this problem? For example, a
lot of careful thought and research has gone into the Perl DateTime
modules.

http://search.cpan.org/dist/DateTime/lib/DateTime.pm#Adding_a_Duration_to_a_Datetime