date and time picker problem, can't reset date or time

Question

I'm using a usoft date time picker control in a dialog box. I started by setting the format to "HH':'mm' 'ddddMMMdd','yyyy" and the current local date & time using DTM-SETSYSTEMTIME. If the user changes any field in the control, the program can not reset the date and time in the control using DTM-SETSYSTEMTIME although SendMessage returns a 1. As far as I can tell, the dialog box returns false (zero) to any notifications it receives concerning the control.

The problem as described above is how I first became aware of it but it's actually much simpler. I did two DTM-SETSYSTEMTIME calls in a row and only the first one took affect. The second in the following example does not get put into effect even though the status is returned is 1.

  hwnd = GetDlgItem (hDlg, IDC_SUN_STAT_DATE_TIME);
  Status = SendMessage (hwnd, DTM_SETFORMAT,0,(LPARAM)"HH':'mm' 'ddddMMMdd','yyyy");
  Status = SendMessage (hwnd, DTM_SETSYSTEMTIME,GDT_VALID, (LPARAM)&systimeTime);
  systimeTime.wHour += 2;
  Status = SendMessage (hwnd, DTM_SETSYSTEMTIME,GDT_VALID, (LPARAM)&systimeTime);

It appears that only the first DTM-SETSYSTEMTIME is put into effect, following ones are ignored.

What do I have to do to change/reset the date/time in the control? Or (more likely) what am I doing wrong?

Answer 1

I have cut and pasted your code into my own program in Visual C++ 6.0, and it works perfectly for me. If I comment out the second DTM_SETSYSTEMTIME, I get a time that is two hours earlier. There is something in the code you're not showing us.

Edit: Since you've selected this answer, I might as well make it accurate. I've verified your comments with my own program.

You're having a problem with the interactions of unexpected behaviors of the date/time picker:

1. The SYSTEMTIME structure requires a full 4-digit year.
2. The date/time picker does not indicate an error if you use DTM_SETSYSTEMTIME with an invalid SYSTEMTIME.
3. Once you've set an invalid SYSTEMTIME, the date/time picker stops responding to further DTM_SETSYSTEMTIME messages. Furthermore it still returns as if it had processed the message properly.