Automatically Rename Sheet Tabs

I have a workbook with multiple tabs. On sheet one a person chooses a date to initialise a formula. That date is then copied to sheet two and placed in cell D5. The date is projected out for two weeks and then the next fornight starts on sheet three and so on. The start date for each new fortnight appears in cell D5 of each sheet. I want that information to be the name of the tab for sheet two, three etc. I have put this code into the "This Workbook" section:

Private Sub Worksheet_Change(ByVal Target As Range)

' Renames all worksheet tabs with each worksheet's cell A1 contents.
'If cell A1 has no content, then that tab is not renamed.

For i = 1 To Sheets.Count
If Worksheets(i).Range("$D$4").Value "" Then
Sheets(i).Name = Worksheets(i).Range("$D$4").Value
End If
Next
End Sub

I have also tried:

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$D$4" Then ActiveSheet.Name = Left(Target.Value, 10)
End Sub

I then go back into sheet one and change the date and nothing happens. I seem to be missing something. Can anyone please help?