Updating date in SQL/VB/Asp.Net

I'm pretty much a novice at all this.. I know bits. Just trying to store a date in an SQL database.. I've set it to "06/06/2015" temporarily in code below to see if I can get it to update but it updates it as 01/01/0001. When I suss it, The value I actually want to store is todays date plus 6 months. EG: if its 31/07/2015 today, I want it to store 31/01/2016. Can anyone help ? Much appreciated...

ASPX.VB

Protected Sub imgBtnDatechange_Click(sender As Object, e As ImageClickEventArgs) Handles imgBtn.Click
Dim acc As New accounts(Membership.GetUser().ProviderUserKey)
Dim adjustedDate as Date = "06/06/2015"
acc.UpdateVipEndDate(acc.accountID, acc.adjustedDate)
End Sub

ACCOUNTS.VB

Public Property adjustedDate As Date

Public Sub UpdateVipEndDate(ByVal accountID As Guid, ByVal adjustedDate As Date)
Dim DBConnect As New DBConn
Using db As DbConnection = DBConnect.Conn("DBConnectionString")
    Dim cmd As SqlCommand = DBConnect.Command(db, "UpdateVipEndDate")
    cmd.Parameters.Add(New SqlParameter("accountID", SqlDbType.UniqueIdentifier,       ParameterDirection.Input)).Value = accountID
    cmd.Parameters.Add(New SqlParameter("newadjustedDate", SqlDbType.Date,     ParameterDirection.Input)).Value = adjustedDate
    db.Open()
    cmd.ExecuteNonQuery()
    cmd.Dispose()
    cmd = Nothing
    db.Dispose()
    db.Close()
End Using

End Sub

STORED PROCEDURE

CREATE PROCEDURE [UpdateVipEndDate]
@accountID          uniqueidentifier,
@newadjustedDate    date
AS
BEGIN

UPDATE tblAccounts SET [vipEndDate] = @newadjustedDate WHERE [accountID] = @accountID

END