Re: [PATCH] SMPP validity

> > In that case the calculation to get the difference in minutes may be
> > more like
> > 
> > (local_tm.tm_year - gmt_tm.tm_year) * 365*24*60 +
> > (local_tm.tm_yday - gmt_tm.tm_yday) * 24*60 +
> > (local_tm.tm_hour - gmt_tm.tm_hour) * 60 +
> > (local_tm.tm_min  - gmt_tm.tm_min );
> 
> Why would I want to handle years and days when I only need the hour
> difference ?

OK, here's why looking only at hours and minutes isn't enough. A country
which is +12 GMT will be identified at 11am as being -12 GMT. Past noon
it will be correctly identified as +12 GMT. Our normalising version
which adds/subtracts 24 hours doesn't work for such a place.

The problem is similar for a place which is -12 GMT.

I believe that it is not a matter of correcting the normalising algorithm
proposed. In fact, this cannot be corrected only by looking at hours
and minutes. So you get into the process of comparing days of the year
as well. That leads to having to compare years as well to account for
wrap arounds on New Year's. That leads to accounting for leap years...

Working with dates is not easy, and one shouldn't assume an "easy"
algorithm will work, and so why go to the bother of using a library
function. I am not lazy at all and will gladly dive into re-implementing
this algorithm for Kannel if it is so desired, and we are prepared to
go through the same amount of testing etc. that the library implementors
have already gone through, to produce something as correct and reliable.

Vibhu

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