[SOLVED] IncMinute after 1800 iteration

[jimbill]

Hello Everyone,

I cant speak very well english 

Lazarus is very good tool.
Congratulations to the developers. And so forth

I would like to announce a behaviour of IncMinute function with thousands of iteration.

If I increment a myDate (:TDateTime) by five minutes (iteration 1 to1800) its doing the incrementation well but after 1791th it's incrementing only 4:59 minutes...
Why do this? Is it expected or not?

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.
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1789. 2017.11.25. 5:00:00
1790. 2017.11.25. 5:05:00
1791. 2017.11.25. 5:10:00
1792. 2017.11.25. 5:14:59
1793. 2017.11.25. 5:19:59
1794. 2017.11.25. 5:24:59
1795. 2017.11.25. 5:29:59
1796. 2017.11.25. 5:34:59
1797. 2017.11.25. 5:39:59
1798. 2017.11.25. 5:44:59
1799. 2017.11.25. 5:49:59
1800. 2017.11.25. 5:54:59

I'am attaching the source code.


windows 7/32 bit  i386-win32-win32/win64

Any help welcome .

Thanks

[Hartmut]

I think this comes because of an accumulated rounding error. Type 'TDateTime' is a double number. For 5 Minutes you always add 5/1440 = 0.0034722...
Try the following, it avoids rounding errors:

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(Sender: TObject);
2. var
3.  HH,MMI,SS,MS: Word;
4.  YY,MM,DD : Word;
5.  myDate,myDate2:TDateTime;
6.  i:integer;
7. begin
8.   DecodeDate(Date,YY,MM,DD);
9.   myDate := EncodeDateTime(YY, MM, DD, 0, 0, 0, 0);
10.  
11.   for i := 1 to 1800 do  begin
12.    myDate2:=IncMinute(myDate,(i-1)*5);
13.    Memo1.Lines.Add(IntToStr(i)+'. '+DateTimeToStr(myDate2));
14.    Application.ProcessMessages;
15.   end;
16. end;  

[jimbill]

Thanks a lot.

It's working.