如何使用delphi xe3更改系统shortdatetime格式

Question

I am going to try and make the question as simple as possible.

How do i either convert the system date to a format i would like, and still keep it a date and not a string. Or how do i get the system's date format, to adjust my dates accordingly.

When i call

FormatShortdateTime('d/M/yyyy',Date);

I get the correct date as string, but cannot convert it back to a Tdate and use it, then it clashes with the system date settings.

If i can get the system shortdate format the problem would be solved.

Answer 1

Update

The answer below refers to the original question that you asked. You've edited the question multiple times now to ask different questions. You really should not do that and it is a sign that you should spend more time understanding the problem before asking questions.

Even so, the final part of the answer, probably still contains the advice that you need. Namely to stop using conversion functions that rely on the global FormatSettings variable, and always use conversion functions that are passed format settings as a parameter.

---

The date values in your database are not stored in the format that you expect. This program:

{$APPTYPE CONSOLE}

uses
  System.SysUtils;

var
  fs: TFormatSettings;
begin
  fs := TFormatSettings.Create;
  fs.ShortDateFormat := 'd/M/yyyy';
  Writeln(DateToStr(StrToDate('18/2/2014', fs)));
end.

produces the following output on my machine:

18/02/2014

I guess on your machine it would produce a different output because your short date format is different from mine. But the point is that the call to StrToDate succeeds.

Clearly the values stored in your database are not in the form you claim. Because you claim that the above code would lead to a date conversion error in the call to StrToDate .

---

Let's step back and look at the initial part of your question:

I would like to know how to convert dates without having the system date influence the software.

The code in the answer above gives you an example of how to do that. Modern versions of Delphi overload the date and time conversion functions. There are overloads that accept TFormatSettings parameters, and overloads without such a parameter. The TFormatSettings parameter is used to control the format used for the conversion. The overloads that do not receive such a parameter use the global FormatSettings instance declared in the SysUtils unit.

What you should do to avoid having the system settings influence your conversions is to only use conversion functions that accept a format settings parameter.

On the other hand, if you want the system settings to influence your conversions, then feel free to call the overloads that use the global format settings variable.

My code above illustrates both. The conversion from string to date requires a fixed format, not varying with local system settings. The conversion from date to string is designed to show a date using the prevailing local system settings.

Answer 2

I would advice creating own TFormatSettings variable

older delphi versions

var
  fs: TFormatSettings;
begin
  fs := TFormatSettings.Create;
  GetLocaleFormatSettings(LOCALE_SYSTEM_DEFAULT, fs);
end.

This will create your own formatSettings (filled with system format) so you won't alter the default one.

Now what's important is that '/' in shortDateFormat will be replaced by dateSeparator so if you do this

fs.ShortDateFormat:='M/d/yyyy';
fs.dateSeparator:='?';

your input should be like this

strtodate('12?30?1899', fs);

or if other way around you will end up with string: '12?30?1899';

I think that your problems originate from that you don't ask what dateSeparator is used. That would lead to problems if what program expects is '30-12-1899' but he gets '30/12/1899' from you.