Private Sub Worksheet_Activate()
Dim F As Worksheet, c As Range, c1 As Range
Set F = Sheets("Séances")
Application.ScreenUpdating = False
[B7:AF12,B16:AF21,B25:AF30].Interior.ColorIndex = xlNone 'RAZ
For Each c In Intersect(F.[B:B], F.UsedRange.EntireRow)
If IsDate(c) Then
If Year(c) = [AC1] Then
Set c1 = Cells.Find(Format(c, "mmmm"), , xlValues, xlWhole) 'mois
c1(3).Resize(6, 7).Find(Day(c)).Interior.Color = c.DisplayFormat.Interior.Color 'colore le jour trouvé
End If
End If
Next
End Sub