在VBA访问中输入参数值错误

我有一个简单的VBA代码，使我可以使用update语句更新数据库表。我要更新的字段是日期/时间，所以我使用的代码是：

Public myDate, renewalDate As Date
Public Sub Renewal()
renewalDate = DLookup("renewalDate", "tblDate", "[id]=1")
Dim newDate As Date
Serial = "123456789"
If Forms![frmRenewal]![txtSerial] = Serial Then
    newDate = DateAdd("m", 1, renewalDate)
    MsgBox newDate
    DoCmd.SetWarnings (False)
    DoCmd.RunSQL "Update tblDate SET tblDate.renewalDate = newDate WHERE (((tblDate.id)=1))"
    MsgBox "You successfully renewed your subscription and renewal date is now " & renewalDate
Else
    MsgBox "Wrong Serial"
End If
End sub

这是数据库表：

当我运行代码时出现此错误