Q189991: PRB: Error Setting DateTimePicker’s Month Programmatically

Article: Q189991
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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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          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version           : WINDOWS:6.0
Issue type        : kbprb

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