Oh, please say you mean 2020!
The seaport hasn't posted that yet. Historically it includes the second weekend in June. If that holds true this year it should be June 11-14, and another website shows those dates.
Bonnie has taken over more responsibilities for the festival (or now that know her better I've become aware of somed responsibilities she's always had). I may see her tomorrow or Monday evenings. If so, I'll ask her. If not, refresh this thread to remind me to email her--or maybe you have her email address.