Para algo como lo anterior una idea es una sentencia VBA, aunque debe personalizar para termine de funcionar de acuerdo a sus necesidades.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim Cell As Range
Dim ws As Worksheet
Set ws = Worksheets("Hoja1")
If Not Intersect(Target, ws.Range("A2:A10")) Is Nothing Or Not Intersect(Target, ws.Range("B2:B10")) Is Nothing Then
Application.EnableEvents = False
For Each Cell In Target
If Not IsEmpty(Cell) And IsNumeric(Cell.Value) Then
If Cell.Column = 1 Then ' Columna A
Cell.Value = DateSerial(2024, 1, Cell.Value)
ElseIf Cell.Column = 2 Then ' Columna B
Cell.Value = DateSerial(2024, 2, Cell.Value)
End If
End If
Next Cell
Application.EnableEvents = True
End If
End Sub