This year's event is over, and it usually runs the 2nd weekend of August to the Last. Definitely follow the web link to find out their future dates:).
You can find out when it starts next year by keeping an eye on its website https://washingtonfaire.com/ The Washington Midsummer Renaissance Faire usually happens, err, Midsummer.
It's usually in August I believe
Unfortunately the event is over for this year.
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