What's the Deal with an NYSE Day-Shift

They NYSE's operating times are a little funky. Most businesses operate from a typical 8-hour, 9-5 day. However, the NYSE's hours come in three flavors (all times are Eastern Standard Time):

The Hour Terminology

• Main Core Market Hours (Where the bulk of everything is traded): a unique 6.5-hour work day. One could say that with main market hours, this is 1.5 hours less than a a typical work day, but I'm sure an actual trader would say that the highly-intense stress levels make that "seemingly" shorter 6.5 hour day, feel much more intense than the typical 8-hour shift.
• Pre-Market Trading: This is where certain stocks or unique orders can be places: An 1.5 of "getting setup trading" so-to-speak from 7-9:30.
  
• After-Market Trading: Again, where unique trades and stocks take place: an extra 4 hours of trading from 4-8pm.
  

The Permutations
Now that we've portrayed the terms, we can focus on discovering the different work-hour permutations. Technically, a trader who works Pre-market trading hours and Main Trading hours every day, would work an 9 shift, albeit from 7-4. An outlier trader (working the pre-market and after-market hours) would work a 6.5 hour shift, the same as the main market hours. This symmetry is interesting. It's unique that the NYSE has an equal number (6.5) of main market hours as it does extended pre- or after-market hours, totally to a 13-hour full day. This is complicated and confusing, especially with something as precise as international trades on the line.

Someone who works All main trading and all after-hours would have an intense 9:30-8pm, 10.5 hour shift. And someone who trades during pre-market, main, and after-hour market times would work from 7-8pm, an insane 13 hour shift. So to clarify, the NYSE IS open 13 hours a day.