[Lazarus] DateDif function needed

Junior lazarus.linux at gmail.com
Sat Nov 16 18:52:12 CET 2013

After all, what would the optimum solution?

Em 16-11-2013 14:40, Michael Van Canneyt escreveu:
> On Sat, 16 Nov 2013, Reinier Olislagers wrote:
>> On 16/11/2013 18:21, Michael Van Canneyt wrote:
>>> On Fri, 15 Nov 2013, Bart wrote:
>>>> The fun part for me is the fact that a seemingly simple question,
>>>> where at first glance you would think "I'll just implement that", can
>>>> lead to so many "problems".
>>> I added a modified version of your implementation to the DateUtils 
>>> unit as:
>>> Procedure PeriodBetween(Const ANow, AThen: TDateTime; Out Years, 
>>> months,
>>> days : Word);
>>> I chose this name because it is more in line with the existing
>>> XXXBetween functions.
>>> I did change the algorithm so it does not do the correction for 
>>> february
>>> of the leap year.
>>> It returns now the same results as the Jedi function. (which I didn't
>>> take for license reasons)
>>> Thanks for providing an implementation.
>> A suggestion if I may: given the wide variation of possibilities of
>> interpretation, some comments in the code about how the calculation is
>> supposed to work would be very much appreciated, I'm sure.
>> (Of course, that applies even more to added documentation).
>> Just wanted to avoid another huge thread discussing PeriodBetween in
>> future... as well as confusion on the part of possible users in general.
> When documenting, all will be explained.
> I think it's fairly simple, really.
> Start with D1. Call this D.
> Keep adding 1 to year of D till your jumps over D2. If you jumped 
> over, substract 1 from year.
> Keep adding 1 to month of D till D jumps over D2. If you jumped over, 
> substract 1 from month.
> Keep adding 1 to day of D till D reaches D2.
> The number of years, months, days you thus added is the period. I may 
> fiddle a bit with the definition of "jumps over" and "reaches", but 
> essentially that is it.
> Michael.
> -- 
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