Hi Oldjay,
Try replacing your code with:
'=============>>
Sub ChangeYear()
Call AddOneYear("J")
Call AddOneYear("K")
End Sub
'<<=============
'=============>>
Sub AddOneYear(col As String)
Dim rng As Range
Dim rcell As Range
Dim WB As Workbook
Dim SH As Worksheet
Dim LRow As Long
Dim CalcMode As Long
Set WB = ThisWorkbook '<<===== CHANGE
Set SH = WB.Sheets("Birthday") '<<===== CHANGE
With Application
CalcMode = .Calculation
.Calculation = xlCalculationManual
.ScreenUpdating = False
End With
LRow = SH.Cells(Rows.Count, col).End(xlUp)
Set rng = SH.Range(col & 2).Resize(LRow - 1)
For Each rcell In rng.Cells
With rcell
If IsDate(.Value) Then
.Value = DateSerial(Year(.Value) + 1, _
Month(.Value), Day(.Value))
End If
End With
Next rcell
With Application
.Calculation = CalcMode
.ScreenUpdating = True
End With
End Sub
'<<=============
Now instead of running the AddOneYear procedure directly, run the ChangeYear
procedure.
In the ChangeYear sub, change J and K to the date columns of interest.