Township regattas are held every week over a six-day period. New regattas start on Tuesdays at 8 am UTC. You need to know your time zone to calculate what time regattas start in your location either by adding or subtracting the time difference.
After a regatta finishes, you have a whole day to rest, switch co-ops, and get ready for the next regatta.
Each season has four regattas. After the season is over, there's a week-long break, during which one interseasonal regatta is held. You can't earn tokens during interseasonal regattas, and the results won't count toward your Golden League leaderboard position, but you can spend tokens that were earned earlier. During interseasonal regattas, you can complete tasks to get chests with rewards and get prizes for reaching co-op goals.
Your co-op stays in the same league during interseasonal regattas, and you can join them at any time once they're on.