Conversation so far:
when did the bucks last win a playoff series?
The Bucks won the playoff series on May 8, 2019.
who was the opponent of the Milwaukee Bucks when they won a playoff series on May 8, 2019?
Boston Celtics
how many games was the playoff series between the Milwaukee Bucks and the Boston Celtics in 2019?
5 games

Question: when was the last playoff series won before 2019?
Self-contained rewrite: when was the last playoff series the Milkwakee Bucks won before 2019?