we got following reply from Aruba support.
Tested few reports in our lab, the date and time values in “Connect Time” and “Disconnect Time” are getting shuffled. When we run the report to export that to a CSV file, the information is fetched from Airwave Database and the transfer of data to the csv file is based on how the data is stored in database. It is the expected behavior that the values can get shuffled based on how it is stored in Airwave Database. Once we have the complete data available on the csv file, the only option to sort this is from csv file in ascending or descending order.
Nithin