Macro création mois puis jours

Sub Struct()
Dim mois As Integer
Dim i As Long
Dim j As Integer
Dim date1 As Date
date1 = "31/12/2008"
mois = Month(date1)
date1 = DateAdd("d", 1, date1)

For i = 1 To 365
    If Month(date1) <> mois Then
        
                ActiveWorkbook.Sheets.Add after:=Worksheets(Worksheets.Count)
                ActiveSheet.Name = Format(Month(date1), "mmmm")
                j = 1
    End If
    Sheets(ActiveSheet.Name).Cells(1, j) = Day(date1)
    date1 = DateAdd("d", 1, date1)
    mois = Month(date1)
    '"Ici ajouter les jours par rapport à la feuille (mois) courante"
    j = j + 1
Next i
End Sub

Option Explicit
Sub test()
Dim a As Integer, m As Byte, sh As Worksheet, j As Date, k As Byte
Application.ScreenUpdating = False
a = "2009"
For m = 1 To 12
    Set sh = Sheets.Add(after:=Sheets(Sheets.Count))
    sh.Name = MonthName(m, True)
    k = 1
    For j = DateSerial(a, m, 1) To DateSerial(a, m + 1, 0)
        sh.Cells(k, 1).Value = j
        k = k + 1
    Next j
Next m
Application.ScreenUpdating = True
End Sub