Conversion failed when converting date and/or time from character string.

 
    Private Sub kaydet() 
          Dim date1, date2, date3 As Date 
          date1 = DateTimePicker1.Value.ToString 
          date2 = DateTimePicker2.Value.ToString 
          date3 = DateTimePicker3.Value.ToString 
          Dim sorgu As String = "insert into ilkyardimcikayitlar (tckimlikno,isimsoyisim,sertifikatipi,sertifikano,isletme,no,egitimbaslangic,egitimbitis,gecerlilik) values('" & TextBox1.Text & "' , '" & TextBox2.Text & "' , '" & TextBox3.Text & "', '" & TextBox4.Text & "', '" & ComboBox1.SelectedIndex & "', '" & TextBox5.Text & "', '" & date1 & "', '" & date2 & "', '" & date3 & "')" 
          komut = New SqlCommand(sorgu, baglan) 
          baglan.Open() 
          komut.ExecuteNonQuery() 
          baglan.Close() 
      End Sub