Re: [gtk-list] Re: adding date/time calculations to glib

[Kenneth Albanowski <kjahds kjahds com>]

On Wed, 7 Oct 1998, Shawn T . Amundson wrote:

> On Wed, Oct 07, 1998 at 02:44:20PM -0500, Jon Trowbridge wrote:
> > I would like to propose that code for doing date and time calculations
> > be added to glib.
> 
> I've given some thought to this recently, with the addition of 
> gtkcalendar to gtk.
> 
> The best C library I've found for this is from the Perl DateCalc 
> module.  The author based the Perl code on C code which has a 
> nice interface, and would be easy to work into glib.  This can
> be found in libgnome/lib_date.[ch] (you might want to make sure
> this is most current).
> 
> One issue with lib_date is it is not internationalized.  That's fixable.
> The month_length and day_name variables should be functions.

month_length? Month_name, surely. :-)

However, a quick glance shows some other slight issues. First, it appears
that the julian routines (among others) won't work correctly with real
Julian (pre-Gregorian) dates, and secondly, none of these routines
understand timezones.

The first issue isn't critical, but it's better to get it right. The
second is actually quite good, as a half-hearted time-zone implementation
is far worse then no timezone logic, IMO. (See the NIH zoneinfo database
at <ftp://elsie.nci.nih.gov/pub/> for a full implementation. As far as I
know, it's the only reasonably comphrehensive set of time-zone data &
logic in the world.) Treating all times as local ("wall clock") is
reasonable in the short run.

And, of course, all of this code only relates to the Gregorian calendar. 

> -Shawn
> 
> 
> >      
> > This is one area where it seems like all sorts of different free
> > programs are constantly reinventing the wheel.  For example, gncal and
> > gnumeric are both using different pieces of code to do basic
> > calculations like the number of days in a month, mapping mm/dd/yyyy
> > dates to julian dates, extracting dates from strings, calculating days
> > of the week, etc.
> >      
> > I'm now in a position where a few different free software projects
> > (guppi, gtk--plot and goose) that I'm working on are also going to
> > need to do date calculations.  Rather than just cutting and pasting
> > the same old code into these projects, I think that we would all be
> > best served if some common code to provide this functionality was set
> > up.
> >      
> > To this end, I'm volunteering to do the work necessary to add this
> > code to glib.  I'd probably use timeutil.{c,h} from gncal as the basis
> > for it, but with improvements and changes to fit it into glib's naming 
> > and coding conventions.  gncal and gnumeric (as well as any other
> > existing code that deals with dates and times) would hopefully be
> > switched over to using the new glib code, but this wouldn't have to
> > happen right away.
> >     
> > -JT
> > 
> > 
> > 
> > 
> > 
> > -- 
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> > 
> --
> Shawn T. Amundson               
> amundson@gimp.org               http://www.gimp.org/~amundson
> 
> "The assumption that the universe looks the same in every
>  direction is clearly not true in reality." - Stephen Hawking
> 
> -- 
> To unsubscribe: mail -s unsubscribe gtk-list-request@redhat.com < /dev/null
> 
> 

-- 
Kenneth Albanowski (kjahds@kjahds.com, CIS: 70705,126)