On Wed, 19 Nov 2014, Philippe wrote:
Em 19.11.2014 12:17, Philippe escreveu:
Em 18.11.2014 10:27, Michael Van Canneyt escreveu:
On Tue, 18 Nov 2014, Philippe wrote:
Em 18.11.2014 09:49, Philippe escreveu: I wrote a program: -
windows 8 32 bits - lazarus 1.2.4 ... fpc 2.6.4 then I copied it to another
computer - windows 7 64 bits - lazarus 1.0.14 .... fpc 2.6.2
and got into trouble with dates format! programs behave diferent way, and what
was working on the fisrt computer does not work properly in
the second! I guess I need some tutorial (I looked for but did not find
anything :( !) why formatDateTime( 'DD/MM/YYYY', now) returns
18-11-2014 and not 18/11/2014 ? strtodate( formatDateTime( 'DD/MM/YYYY',
now)) works ok on the w 8 32 bits, but arise an exception on
the w 7 64 bits. I am confused with the following syntax function
FormatDateTime( const FormatStr: string; DateTime:
TDateTime; const FormatSettings: TFormatSettings ):string; how does it work
between two format especifications: FormatStr and
FormatSettings ? appreciate any example of good programming pratise of data
formating to
avoid bad surprise moving program from an OS to another !
Philippe on http://www.freepascal.org/docs-html/rtl/sysutils/strtodate.html I
found Program Example19; { This program demonstrates the
StrToDate function } Uses sysutils; Procedure TestStr (S : String); begin
Writeln
(S,' : ',DateToStr(StrToDate(S))); end; Begin Writeln
('ShortDateFormat ',ShortDateFormat); TestStr(DateTimeToStr(Date));
TestStr('05'+DateSeparator+'05'+DateSeparator+'1999');
TestStr('5'+DateSeparator+'5'); TestStr('5'); End. the compiler warns that
ShortDateFormat is deprecated ... which is not informed in
the doc ...
It should be, I will check.
Anyway, as Graeme hinted: ShortDateFormat contains a format string, and / is a placeholder for the date
separator character on the computer on which the program is running.
If you want to force a character, you can enclose it in quotes:
ShortDateFormat:='dd"/"mm"/"yyyy'
will always use / as the date separator, no matter what the internatonalization
settings on the PC.
But it is bad practice to do so.
Secondly, it is a common mistake to think that StrToDate will always correctly
perform the opposite of DateToStr.
It does not, but this is documented.
Michael.
I still don't know how to use at the same time formatStr and FormatSettings in
FormatDateTime.
I´ll like very much to find a tutorial or some example about the good practice
to manage dates and be sure it will do the same thing on different machines ....
Good practice is to avoid converting to and from string the whole time.
If you need to store a timestamp, use the ISO 8601 format or RFC 3339 (or is it
3999?).
Regarding formatsettings:
Since some versions, most date/time/money/float formatting routines support
passing a TFormatSettings record to it to control the formatting.
(this is mostly done for multi-threaded apps where different threads can have
different settings, like in web-apps).
If no TFormatSettings record is passed, the global FormatSettings record is
used.
The various format variables which existed prior to this change,
have simply been moved to this global FormatSettings record, with some backwards compatibility code.
So if you had old code that did something like:
ShortDateStr:='dd/mm/yyyy';
you should now use
FormatSettings.ShortDateStr:='dd/mm/yyyy';
That is all there is to it. Hardly worth a tutorial.
But if you have suggestions for the documentation, I will be glad to add them.
Michael.
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