SelecteIndex Changed doesn't work - asp.net

Question

I have a little problem that bothers me presently. I have 5 dropboxes which I populate dynamically:
date
month(letter)
year
numeric-date 5 numeric-month.
I populate them with a current date values using folowing code:
Dim CurYear As Integer = DatePart("yyyy", Now)
Dim CurDate As Integer = DatePart("d", Now)
Dim CurMonth As String = Format(Today.Date, "MMMM")
Dim CurDate2 As Integer = DatePart("d", Now)
Dim CurMonth2 As String = Format(Now, "MM")
Dates.Text = CurDate
Monthe.Text = CurMonth
years.Text = CurYear
Month2.Text = CurMonth2
Dates2.Text = CurDate2
Than I have an update panel which handles boxes 4 and 5. They should change the Index if the boxes 1 and 2 are changed. But it doesn't work.
Protected Sub Months_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles Months.SelectedIndexChanged
Month2.SelectedIndex = Months.SelectedIndex
End Sub
Protected Sub Dates_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles Dates.SelectedIndexChanged
Dates2.SelectedIndex = Dates.SelectedIndex
End Sub
If I don't populate the drop boxes with a current date (code sample 1) it works. If I do, selectedIndexChanged doesn't react. What can be the possible mistake?
asp markup:
<asp:DropDownList ID="Dates" runat="server" autopostback="true">
<asp:ListItem></asp:ListItem>
<asp:ListItem>1</asp:ListItem>
...
<asp:ListItem>26</asp:ListItem>
<asp:ListItem>27</asp:ListItem>
<asp:ListItem>28</asp:ListItem>
<asp:ListItem>29</asp:ListItem>
<asp:ListItem>30</asp:ListItem>
<asp:ListItem>31</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="Months" runat="server" autopostback="true" >
<asp:ListItem></asp:ListItem>
<asp:ListItem>January</asp:ListItem>
...
<asp:ListItem>November</asp:ListItem>
<asp:ListItem>December</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="years" runat="server" autopostback="true" >
<asp:ListItem></asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="Dates2" runat="server" AutoPostBack="True">
<asp:ListItem></asp:ListItem>
<asp:ListItem>01</asp:ListItem>
<asp:ListItem>02</asp:ListItem>
....
<asp:ListItem>29</asp:ListItem>
<asp:ListItem>30</asp:ListItem>
<asp:ListItem>31</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="Month2" runat="server" AutoPostBack="True">
<asp:ListItem></asp:ListItem>
<asp:ListItem>01</asp:ListItem>
....
<asp:ListItem>11</asp:ListItem>
<asp:ListItem>12</asp:ListItem>
</asp:DropDownList>