Microsoft KB Archive/189991

Knowledge Base

PRB: Error Setting DateTimePicker's Month Programmatically

Article ID: 189991

Article Last Modified on 1/9/2003

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APPLIES TO

• Microsoft Visual Basic 6.0 Professional Edition
• Microsoft Visual Basic 6.0 Enterprise Edition

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This article was previously published under Q189991

SYMPTOMS

When you try to programmatically set the Month property of a DateTimePicker control, you receive the following error message:

"Run-time error '380': Invalid property value"

If you use the drop-down Calendar to change the Month for the same date, it works correctly.

CAUSE

When you change the Month property through the DateTimePicker control's Calendar interface, it handles adjusting the Day property to create a valid date. But if you assign a value to the Month property in code and this creates an invalid date, you receive the appropriate error message.

RESOLUTION

Check to ensure that the combination of the control's current Day and Year, along with the Month you wish to assign, combine to create a valid date.

Another approach you can take is to use the DateAdd function to change the value of the Month property of the DateTimePicker control by adding or subtracting the appropriate number of months. Just like the control's graphic interface, the DateAdd function will automatically adjust for differences in the number of days in the various months.

STATUS

This behavior is by design.

MORE INFORMATION

When changing the Month interactively, the DateTimePicker allows for the fact that some months are shorter than others and adjusts the Day property, making it smaller if necessary. If the Month is changed programmatically this interface is bypassed and an invalid date can result. While it is possible to write code that will check for valid dates and adjust the Day property when necessary, it is much simpler to use the DateAdd function to change the date. The following sample demonstrates the problem and a solution.

Steps to Reproduce Behavior

1. Create a new Standard EXE project. Form1 is created by default.
2. Select Components from the Project menu, check "Microsoft Windows Common Controls-2 6.0," and then click OK.
3. Place a CommandButton and a DTPicker control onto Form1.

4. Place the following code into the module of Form1:

         Private Sub Form_Load()
            DTPicker1.Value = "1/29/97"
         End Sub
   
         Private Sub Command1_Click()
            DTPicker1.Month = 2
            ' Comment the line above and uncomment the line below to test fix
            'DTPicker1.Value = DateAdd("m", 1, DTPicker1.Value)
         End Sub
   
                           

5. Run the project, note the date is 1/29/97, and click on Command1. You will see "Run-time error '380': Invalid property value". This is because 2/29/98 is not a valid date.
6. Stop the project.
7. Comment the Month assignment line, uncomment the line that calls the DateAdd function and run the project. Click on Command1 and the date advances one month properly, to 2/28/97.
   
   You can retry this test using dates like 7/31/98 for an initial value and try to assign a value of 6 to Month. Any value that corresponds to a Month with fewer than 31 days will generate the error. You can use positive or negative values in the DateAdd function, so it can subtract months as easily as it adds them.

Additional query words: kbDSupport kbDSD kbVBp kbVBp600 kbCtrl

Keywords: kbprb KB189991

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