[Haskell-cafe] Re: why doesn't time allow diff of localtimes ?

[briand at aracnet.com]

On Thu, 01 Apr 2010 06:20:25 +0200
Maciej Piechotka <uzytkownik2 at gmail.com> wrote:

> On Wed, 2010-03-31 at 19:29 -0700, briand at aracnet.com wrote:
> > On Wed, 31 Mar 2010 01:32:56 -0400
> > wagnerdm at seas.upenn.edu wrote:
> > 
> > > Two values of LocalTime may well be computed with respect to
> > > different timezones, which makes the operation you ask for
> > > dangerous. First convert to UTCTime (with localTimeToUTC), then
> > > compare.
> > 
> > that makes sense.  unfortunately getting the current timezone to
> > convert to UTC results in the dreaded IO contamination problem...
> > 
> > Brian
> 
> Hmm. Where do you get the local times from in the first place?
> 

read it from a file of course :-)

I think I've got it figured out.  it's not too ugly.

One interesting "hole" in the system is that buildTime can return a
LocalTime _or_ a UTCTime.  That means the same string used to
generate a time can give you two different times.

It seems as thought it should be restricted to always returning a
UTCTime.  If it's going to return a local time it should require an
extra argument of a timezone, shouldn't it ?

Brian