Today I’m going to show you how to create a simple Date Calculator in Visual Basic 2008.With this, it will help you know the dates before and after the present date. For instance, you want to jump into seven days after the present date, the date calculator will automatically calculate it. And you don’t have to count the days anymore.

So lets begin:

Open Visual Basic 2008, create a new Windows Application and do the Form just like this. Name the two textboxes, the first is “txtafter” and the other one is “txtbefore” and the DateTimePicker is “dtpstrdate”.



Double click the Form and do the following code above the Form_Load

for declaring the variables.

1. 'DECLARING THE VARIABLES
   
2. Dim
   
   intervaldate As
   
   Integer
   
   'REPRESENTS A DATE INTERVAL
   
3. Dim
   
   dateresult As
   
   Date
   
   'REPRESENTS THE ADDED DATE OF START DATE AND THE INTERVAL DAYS
   
4. Dim
   
   msg As
   
   String
   
   'REPESENTS A MESSAGE TO PUT INTO A LISTBOX
   

Then, go back the Design Views, double click the Textbox(txtafter) and do the following code.

1. Private
   
   Sub
   
   txtafter_TextChanged(
   
   ByVal
   
   sender As
   
   System.
   
   Object
   
   , ByVal
   
   e As
   
   System.
   
   EventArgs
   
   )
   
   Handles
   
   txtafter.
   
   TextChanged
   
2. Try
   
3. 'CONDITIONING THE AFTER DAYS INTERVAL
   
4. If
   
   txtafter.
   
   Text
   
   .
   
   Length
   
   >
   
   0
   
   Then
   
   'CHECK THE INTERVAL DAYS IF GREATER THAN 0.
   
5. intervaldate =
   
   CInt
   
   (
   
   txtafter.
   
   Text
   
   )
   
   'ASSIGNING A TEXTBOX TO A VARIALBLE
   
6. 'FORMULA
   
7. dateresult =
   
   dtpstrdate.
   
   Value
   
   .
   
   AddDays
   
   (
   
   intervaldate)
   
   .
   
   ToString
   
   (
   
   )
   
   'ADDING THE INTERVAL DAYS TO THE START DATE.
   
8. msg =
   
   "After "
   
   &
   
   intervaldate &
   
   " day(s), the date is "
   
   'MESSAGE TO BE PUT IN THE LISTBOX
   
9. ListBox1.
   
   Items
   
   .
   
   Clear
   
   (
   
   )
   
   'CLEARING A LISTBOX
   
10. ListBox1.
    
    Items
    
    .
    
    Add
    
    (
    
    msg &
    
    Format
    
    (
    
    dateresult, "dddd, MMMM dd, yyyy"
    
    )
    
    )
    
    'ADDING A MESSAGE AND FORMATTED DATE RESULT IN THE LISTBOX
    
11. txtbefore.
    
    Clear
    
    (
    
    )
    
    'CLEARING THE TEXTBOX
    
12. Else
    
13. ListBox1.
    
    Items
    
    .
    
    Clear
    
    (
    
    )
    
    'CLEARING A LISTBOX
    
14. End
    
    If
    
15. Catch
    
    ex As
    
    Exception
    
16. MsgBox
    
    (
    
    ex.
    
    Message
    
    )
    
17. End
    
    Try
    
18. 
    
19. 
    
20. End
    
    Sub
    

After that, go back to the Design Views again, double click the Textbox(txtbefore) and do the following code.

1. Private
   
   Sub
   
   txtbefore_TextChanged(
   
   ByVal
   
   sender As
   
   System.
   
   Object
   
   , ByVal
   
   e As
   
   System.
   
   EventArgs
   
   )
   
   Handles
   
   txtbefore.
   
   TextChanged
   
2. Try
   
3. 'CONDITIONING THE BEFORE DAYS INTERVAL
   
4. If
   
   txtbefore.
   
   Text
   
   .
   
   Length
   
   >
   
   0
   
   Then
   
5. intervaldate =
   
   CInt
   
   (
   
   txtbefore.
   
   Text
   
   )
   
6. 'FORMULA
   
7. 'SYNTAX...
   
8. 'THE FORMULA IS THE SAME BUT THE TWIST IS
   
9. 'I ADD A NEGATIVE INTERVAL SO THAT IT WILL GO BACK TO THE PREVIOUS DATE.
   
10. dateresult =
    
    dtpstrdate.
    
    Value
    
    .
    
    AddDays
    
    (
    
    -
    
    intervaldate)
    
    .
    
    ToString
    
    (
    
    )
    
11. msg =
    
    "Before "
    
    &
    
    intervaldate &
    
    " day(s), the date is "
    
12. ListBox1.
    
    Items
    
    .
    
    Clear
    
    (
    
    )
    
13. ListBox1.
    
    Items
    
    .
    
    Add
    
    (
    
    msg &
    
    Format
    
    (
    
    dateresult, "dddd, MMMM dd, yyyy"
    
    )
    
    )
    
14. txtafter.
    
    Clear
    
    (
    
    )
    
15. Else
    
16. ListBox1.
    
    Items
    
    .
    
    Clear
    
    (
    
    )
    
17. End
    
    If
    
18. Catch
    
    ex As
    
    Exception
    
19. MsgBox
    
    (
    
    ex.
    
    Message
    
    )
    
20. End
    
    Try
    
21. End
    
    Sub
    

You can download the complete source.

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