Sessions are only to be used for a single day in a single Time Entry. Do not create sessions for multiple different days inside of one Time Entry. Sessions are not meant to be used like that and will cause problems. Sessions are primarily meant to keep track of your "punch in & out" times during a single working day. Only the "sum" of the durations for Sessions will be "rounded" in the main time entry. This allows you to do many short sessions, but round the main Time Entry as a whole. We cannot restrict the date because some workers may start late at night and work into the next morning, otherwise we would. Time Entries allow a maximum time of 24 hours, thus the sessions must be less than 24 hours.
So when using sessions, you must create a new Time Entry for any subsequent days, with it's own session for that day. Hope that makes sense?