Q. In the Flows Settings > About window, the database size is displayed as 242 GB. The current database information indicates the database spans ~14,785 days. How can that be possible?
A. This is caused by one or more sessions being marked with a start date of 0 -- this corresponds to Unix epoch, January 1, 1970. This error can be caused by receiving a malformed netflow record, or possibly through database corruption or a mistake in the incoming session hash -- we are investigating what could cause this to happen. Other than potentially a missing session (it may just be one update that was mis-reported or mis-handled, which would mean that the whole session is not lost and you aren't missing any data) there is no harm to it, and the bad session record will eventually be flushed out of the database once the database is full.
If you are curious about those sessions, you can set the time to 00:00 January 1st, 1970 to see what sessions are reported there. (Note: the server cannot return values before then, and may disconnect clients that try, as dates before then are treated as negative numbers)