Here is information from the State of Hawaii Office of Elections on voter registration:
Beginning with the 2020 Elections, Hawaii votes by mail and all voters will automatically receive their ballot in the mail 18 days prior to each election.
Primary Election Ballot Delivered: July 21, 2020
Primary Election: August 8, 2020
General Election Ballot Delivered: October 16, 2020
General Election: November 3, 2020