[Gambas-user] Format function changes date value

[Benoît Minisini]

Le 07/06/2018 à 11:55, George a écrit :
> It's not a lack of understanding on my part.  I have developed software 
> that must work across different time zones, and it certainly adds a 
> layer of complication to things, since time data must be dealt with 
> based on location, and display of times must take into account the 
> user's location (showing everything as GMT is the lazy way out, as it 
> puts the burden of time conversion on the user.)
> 
> However, in this particular case I'm working with data that's in a 
> single location, and only deals with days, not times.  That should be 
> easy, since it shouldn't need to deal with time zones.  And yet, due to 
> the way date functions work, what should be a simple calculation, such 
> as how many days are between 1-Jun-2018 and 3-Jun-2018, needs to know 
> the GMT offset of the machine it's running on, and fudge the date into a 
> date/time value in order to get the correct result. (Just changing 
> CDate() to Date(), as previously suggested, did not work for me.)  Yes, 
> that can be done, but because of what that would have entailed, in this 
> case I decided that porting the app to a different language was the 
> better option for me.

You get the difference between two dates with DateDiff(). Where did you 
see that you had to deal with timezones?

> 
> IMHO all date functions should work internally as based on GMT or local 
> time, not a mix of both.  

All date & times are internally stored in UTC.

But all date & times functions that deal with date & time string printed 
representation (Str & Val & Format) have to supposed a local date, 
because none of them have an optional argument that would tell the timezone.

Date & times functions using a non-printed string representation (CStr & 
CDate) assume an UTC timezone.

-- 
Benoît Minisini