how long has the wind storm on Jupiter(The Red Dot) lasted?

Question: how long has the wind storm on Jupiter(The Red Dot) lasted?
- Keywords:
  Great Red Spot,
  Jupiter,
  storm
Asked by Sheldon Cooper to Anne, Beth, COLFlight, Jon, Tom on 15 Oct 2015.
- Beth Healey answered on 15 Oct 2015:
  
  Hi Sheldon!
  
  The Red Spot is a giant oval-shaped anticyclonic storm. I’m not sure exactly how long it has been there but several centuries at least.
  
  Recently a new red spot, called Oval BA (nickname Red Jr) has also been found and its progress is being tracked.

Question: how long has the wind storm on Jupiter(The Red Dot) lasted?