[fpc-pascal] DateTimeToUnix bug?

[John Coppens]

On Tue, 30 Dec 2008 09:25:29 -0700
"Seth Grover" <sethdgrover at gmail.com> wrote:

> It seems to me that 09-16-1989 12:00:01 should be 621950401, not
> 621950400.

This seems to be rounding error - if you put 1 ms (milisecond) in the
seconds test, the result comes out right. For consecutive seconds, and
ms = 0:

09-16-1989 12:00:00 = 621950400 = 09-16-1989 12:00:00
09-16-1989 12:00:01 = 621950400 = 09-16-1989 12:00:00
09-16-1989 12:00:02 = 621950402 = 09-16-1989 12:00:02
09-16-1989 12:00:03 = 621950403 = 09-16-1989 12:00:03
09-16-1989 12:00:04 = 621950403 = 09-16-1989 12:00:03
09-16-1989 12:00:05 = 621950404 = 09-16-1989 12:00:04
09-16-1989 12:00:06 = 621950406 = 09-16-1989 12:00:06
09-16-1989 12:00:07 = 621950407 = 09-16-1989 12:00:07
09-16-1989 12:00:08 = 621950407 = 09-16-1989 12:00:07
09-16-1989 12:00:09 = 621950408 = 09-16-1989 12:00:08
09-16-1989 12:00:10 = 621950410 = 09-16-1989 12:00:10
09-16-1989 12:00:11 = 621950411 = 09-16-1989 12:00:11
09-16-1989 12:00:12 = 621950411 = 09-16-1989 12:00:11
09-16-1989 12:00:13 = 621950412 = 09-16-1989 12:00:12

with ms = 1:

09-16-1989 12:00:00 = 621950400 = 09-16-1989 12:00:00
09-16-1989 12:00:01 = 621950401 = 09-16-1989 12:00:01
09-16-1989 12:00:02 = 621950402 = 09-16-1989 12:00:02
09-16-1989 12:00:03 = 621950403 = 09-16-1989 12:00:03
09-16-1989 12:00:04 = 621950404 = 09-16-1989 12:00:04
09-16-1989 12:00:05 = 621950405 = 09-16-1989 12:00:05
09-16-1989 12:00:06 = 621950406 = 09-16-1989 12:00:06
09-16-1989 12:00:07 = 621950407 = 09-16-1989 12:00:07
09-16-1989 12:00:08 = 621950408 = 09-16-1989 12:00:08
09-16-1989 12:00:09 = 621950409 = 09-16-1989 12:00:09
09-16-1989 12:00:10 = 621950410 = 09-16-1989 12:00:10
09-16-1989 12:00:11 = 621950411 = 09-16-1989 12:00:11
09-16-1989 12:00:12 = 621950412 = 09-16-1989 12:00:12

John

I slightly modified the test program:

program Project1;

uses
  Classes,
  SysUtils,
  DateUtils;

var
  utime  : longword;
  sec : word;
  currentDt : TDateTime;
  convertedDt : TDateTime;

begin
  for sec := 0 to 59 do begin
    currentDt := EncodeDateTime(1989, 9, 16, 12, 0, sec, 1);
    utime := DateTimeToUnix(currentDt);
    convertedDt := UnixToDateTime(utime);
    writeln(FormatDateTime('mm/dd/yyyy HH:nn:ss', currentDt) + ' = ' +
      IntToStr(utime) + ' = ' +
      FormatDateTime('mm/dd/yyyy HH:nn:ss',
      convertedDt));
  end;
end.