Excel VBA 减去两个日期以计算整个列中的天数

Question

I am trying without a positive result a function that calculates difference in days between days in Column "B", B2:B range and today date that is in cell "K2" and results are being transferred into in column 7, range: G2:G. So far I am getting more and more excited about VBA coding, but as a person that needs more exp in this I would like to ask for some help about solving this issue.

Sub DateSub()
    Dim strInput As String, strOutput As String
    Dim start_date As Date
    Dim end_date As Date
    Dim diff As Integer
    
   Dim LastRowcheck As Long, n1 As Long
    Sheets("T1").Range("K2") = Format(Date, "DD-MM-YY") 'today
    end_date = Sheets("T1").Cells(2, 11).Value
    LastRowcheck = Sheets("T1").Range("B" & Rows.Count).End(xlUp).Row

  For n1 = 1 To LastRowcheck
    With Worksheets("T1").Cells(n1, 2)
        start_date = Sheets("T1").Cells(n1, 2).Value
        diff = DateDiff("D", start_date, end_date) ' HERE IS ISSUE
        Cells(nl + 1, 2) = diff
        Sheets("T1").Cells(n1 + 1, 7).Select
        Selection.NumberFormat = "dd-mm-yy"
        
   End With
  Next n1
    Application.DisplayAlerts = False

End Sub

Answer 1

Not sure if it's the cause of your overflow, however be aware of the following. Especially working with dates, you can easily get an overflow error if using the Integer data type.

Per the documentation for VBA Data type's ;

Integer 2 bytes -32,768 to 32,767

Change your data type for diff to Long - Dim diff As Long .

Long (Long integer) 4 bytes -2,147,483,648 to 2,147,483,647

Answer 2

Insert the date value , not a formatted string:

Sheets("T1").Range("K2") = Date 'today

Apply the date format to K2.

Answer 3

Sub DateSub()
    Dim strInput As String, strOutput As String
    Dim start_date As Date
    Dim end_date As Date
    Dim diff As Integer
    Dim LastRowcheck As Long
    Dim n1 As Long
    Sheets("T1").Range("K2") = Format(Date, "DD-MM-YYYY") 'today
    end_date = Sheets("T1").Cells(2, 11).Value
    LastRowcheck = Sheets("T1").Range("B" & Rows.Count).End(xlUp).Row
    Sheets("T1").Activate
    For n1 = 2 To LastRowcheck
        start_date = Sheets("T1").Cells(n1, 2).Value
        diff = DateDiff("D", start_date, end_date) 
        Cells(n1, 3) = diff
        Cells(n1 + 1, 7).Select
        Selection.NumberFormat = "dd-mm-yy"
    Next n1
    Application.DisplayAlerts = False
End Sub

Above codes works fine and is tested. Few things changed and corrected.

1. Cells(nl + 1, 2) = diff will overwrite the next row in same column with diff, this should be shifted to next column

2. Format(Date, "DD-MM-YY") changed to YYYY to avoid confusion of 19th or 20th century

3. with is not required

4. I have changed the for loop to start from row 2, you can change it back to 1, but make sure that its not empty otherwise you will get overflow error