Show and tell: Last-Yearify (Happy new year! )

I work in accounts, and I'm still entering transactions for 2024. If you enter just day and month into excel, it will assume this year. I get to the bottom of a column and see I've accidentally missed the year of a few dates and need to correct them.

I got frustrated and made the following.

Sub LastYearify()

' Purpose: Checks if the selected cell is a date, and pushes that date into last year.
' Origin: Created by Joseph in 2024. No wait, 2025.

Dim thisCell As Integer
Dim CellCount As Integer
Dim myRange As Range
Dim myCell As Range

On Error GoTo Errorhandler

Set myRange = Application.Selection
CellCount = myRange.Cells.Count

For thisCell = 1 To CellCount
    Set myCell = myRange.Cells(thisCell)
    If IsDate(myCell.Value) Then
        myCell.Value = DateSerial(Year(Now()) - 1, Month(myCell.Value), Day(myCell.Value))
    Else
        Debug.Print myCell.Address & " - Not a date."
    End If
    Set myCell = Nothing

Next thisCell
Exit Sub

Errorhandler:
MsgBox ("There has been an error. Sorry.")


End Sub