I had the same problem and I did not find any solution on internet.
So I wrote this procedure.

Sub Y1904()

For Each Sht In ActiveWorkbook.Sheets
Set Rng = Sht.UsedRange
For Each cell In Rng
If cell.HasFormula = False Then
If IsDate(cell.Value) Then
cell.Value = cell.Value + 1462
End If

End If

Next
Next
End Sub

Basically it adds to all cells containing a date (not formula) the 1462 value.