Error 6: Overflow; Dim as long already?

[Rogue909]

So I have a with loop....

Dim i As Long

 For i = 1 To 4000        If CalibSource.Cells(i, 1).Value = "1/2/2013" Then
            CalibSource.Range(CalibSource.Cells(i, 1), CalibSource.Cells(i, 15)).Copy
            CalibSh.Range("A" & CalibSh.Cells(Rows.Count, 1).End(xlUp).Row + 1).PasteSpecial Paste:=xlPasteValues
        End If
    Next i

If I change the "For i=1 to 4000" to 5000 (to increase the search range) than I immediately get an error 6 overflow.

My research has indicated that this is because i is not called as an integer... however it clearly is?

What is it that I am missing? Unfortunately I need to have a search range larger than 4000 rows so I need to figure this out.

 

[RoryA]

If the cell contains an actual date, you can just refer to its Value/Value2 property directly, no need for DateSerial.