Sub RenameSheetsToMonths()
Dim i As Integer
Dim monthNames As Variant
monthNames = Array("January", "February", "March", "April", "May", "June", _
"July", "August", "September", "October", "November", "December")
For i = 1 To 12
If ThisWorkbook.Sheets.Count >= i Then
ThisWorkbook.Sheets(i).Name = monthNames(i - 1)
Else
' Add new sheet if not enough
ThisWorkbook.Sheets.Add After:=Sheets(ThisWorkbook.Sheets.Count)
ThisWorkbook.Sheets(ThisWorkbook.Sheets.Count).Name = monthNames(i - 1)
End If
Next i
End Sub