unsupportedformatexception in Xojo

For the sake of troubleshooting, try this

dim v as variant = rs.Field("dateAcc").Value
dim s as string = rs.Field("dateAcc").StringValue
dim d as date = rs.Field("dateAcc").DateValue

Run it in the debugger and when it triggers the exception, examine the values of v and s. What is in the column? Maybe examine the rest of the values and make note of the primary key. Use that to select the record in a query viewer and see what it thinks is in the column.