USA-Swimming updates Zone (National AAA) cuts each quadrennium as part of the Motivational National Time Standards. 

The complete list of 2017-2020 National Motivational Time Standards can be found at the link below (National B, BB, A, AA, AAA, AAAA). "ZONE" are the "AAA" standards shown for Long Course Meters and Short Course Yards.

• Qualifying for this National meet - National AAA in either SCY or LCM

There are three standards lists:  Long Course Meters (50-meter pool, LCM), Short Course Yards (25-yard pool, SCM), and Short Course Meters (25-meter pool, SCM).  You qualify for Zones if you have a AAA cut in any pool within the qualifying period which is generally one year before the Zone meet.