Baseball’s offseason is really triggered by the end of the World Series. Several key dates hinge on that moment.
The off day between Games 2 and 3 of the World Series.
Immediately after the World Series
Eligible players become free agents
Fifth day after World Series
Last day to make a qualifying offer to free agents Players have seven days to accept or decline a qualifying one-year offer
Sixth day after World Series
First day free agents can sign with teams other than their former teams
General Manager meetings in California
Twelvth day after World Series
Last day for a player to accept arbitration from former club (by midnight ET)