How to read both Date and Time from a TDateTimePicker

Question

I'm really confused. What I want to do (seems pretty simple) is to display a date + time in a TDateTimePicker, with the calendar integrated, and be able to read it after its value has changed.

I'd like to use the dd/MM/yyyy hh:mm format.

Since the TDateTimePicker isn't a TDateOrTimePicker, a used one with :

• Kind : dtkDate (displays the calendar)
• Format : 'dd/MM/yyyy hh:mm'

Looks good, now let's read it :

showmessage(DateTimeToStr(DateTimePicker1.Date)); 

Only displays the date correctly. Changes on the hh:mm part is not taken into account. I always get the default value. Then I thought : There is also a Time property, maybe I need to read the value in 2 times.

 showmessage(DateTimeToStr(DateTimePicker1.Time));
 showmessage(DateTimeToStr(DateTimePicker1.Date));

But I have the exact same output (and problem) as before. So now, let's try to change this Kind property to dtkTime, then read the time, then switch it back to dtkDate then read the date.

But no, it still doesn't work. Switching the Kind property from dtkDate to dtkTime erases my input on the hh:mm part.

---

I know I'm actually supposed to work with 2 TDateTimePickers : one for the date, one for the time.

So my question is :

• Is there an easy way to solve my simple and very common problem (a real DateTimePicker) ?

And a Delphi design questions :

• Why is there a Format property that is basically useless and misleading ? Having a TimeFormat, DateFormat, and proper format validation process isn't that hard.

Please note that I post this question mainly to avoid beginners doing the same loooong process of debugging and frustration.

Answer 1

What I want to do (seems pretty simple) is to display a date + time in a TDateTimePicker, with the calendar integrated, and be able to read it after its value has changed.

I'd like to use the dd/MM/yyyy hh:mm format

Sorry, but you cannot. A TDateTimePicker is designed to only work with EITHER a date OR a time, but not BOTH.

If you set the Kind property to dtkDate, you can specify a custom DATE format but any TIME format is ignored, and using the Time property is undefined.

If you set the Kind property to dtkTime, you can specify a custom TIME format but any DATE format is ignored, and using the Date property is undefined.

When reading the Date property, only the DATE portion of the value is valid. In a perfect world, the TIME portion will always be zero, but I have seen it contain garbage sometimes. However, you can easily ignore that using the DateUtils.DateOf() function:

Value := DateOf(DateTimePicker1.Date);

Same thing with the Time property and the DATE portion of the value. You can use the DateUtils.TimeOf() function to ignore any potential garbage:

Value := TimeOf(DateTimePicker1.Time);

Is there an easy way to solve my simple and very common problem (a real DateTimePicker) ?

The only real solution with TDateTimePicker is to use two separate TDateTimePicker controls, one for a date the other for a time. You can combine the two values together when needed:

Value := DateOf(DateTimePicker1.Date) + TimeOf(DateTimePicker2.Time)

If you want to display a TDateTime, just do the opposite:

DateTimePicker1.Date := DateOf(Value);
DateTimePicker2.Time := TimeOf(Value);

Otherwise, find a 3rd party picker (or write your own) that supports what you need.

Why is there a Format property that is basically useless and misleading ?

It is not useless and misleading. It is perfectly useful, but only within the confines of the current Kind setting.

Having a TimeFormat, DateFormat, and proper format validation process isn't that hard.

TDateTimePicker is just a thin wrapper for a Win32 Date and Time Picker control, which has no such functionality. Certainly they could have written custom logic to allow switching between the Kind values with different setups preserved, but that is not really how a DTP control is meant to be used. You set the Kind once, the Format once, and then handle input and output as needed. No switching back and forth. Just because you can switch the Kind dynamically doesn't mean you should. If you think writing such custom logic is easy, you are welcome to do it in your own code.

Answer 2

I have exactly the same issue. Andre solution works like a charm thanks to Andre).

ISSUE : We need to create a new unit, create a new component and register the component to another package to be able to setup the form at desgin time.

SOLUTION : To avoid this, just declare in the form where you are using TDateTimePicker component the following class : THackDateTimePicker

...
type
  // this class is just to access protected Caption property
  THackDateTimePicker = class(TDateTimePicker);

  TSymbolInfoForm = class(TForm)
  ...
end;

Then just implement OnChange event like :

procedure TSymbolInfoForm.dtpChange(Sender: TObject);
begin
   TDatetimePicker(Sender).Datetime := StrToDateTime(THackDateTimePicker(Sender).Caption);
end;

you can link all OnChange event of all TDateTimePicker components on the same form to the sane OnChange event... and voila!

Answer 3

I had the same frustrating problem these days. But in my case I just needed to get the complete Date and Time from the TDateTimePicker field (didn't needed to set it programatically, but it would not be very difficult). So what I did is to create my own TDateTimePicker and create a new public property that gets the field Caption and sets into DateTime (Caption is protected accordind to the documentation). Here's my code:

unit uZDateTimePicker;

interface

uses
 Vcl.ComCtrls, SysUtils;

type
  TZDateTimePicker = class(TDateTimePicker)
  private
    procedure SetDateAndTime;

  protected
    procedure Change; override;

  end;

implementation

{ TZDateTimePicker }

procedure TZDateTimePicker.Change;
begin
  SetDateAndTime
end;

procedure TZDateTimePicker.SetDateAndTime;
begin
  DateTime := StrToDateTime(Caption);
  inherited;
end;


end.

As simple as that.

Also, if you use the DevExpress components you would use the TcxDateEdit that works just like you want.

Answer 4

The above answers are all in correct , you can get datetime from the datetimepicker.DateTime Property , you can show date and time by setting the "Format" property too dd/MM/yyyy hh:mm