Chatter from r/churning:
Possible to fly to Hawaii in a day, impossible coming back since SW does not fly overnight. Have to stop in Cali and then fly back to east the next day.
Edit: Possible to book in a single day, cannot book from ATL, MCO, FLL, etc direct to Hawaii as it comes back with an error. Was able to find from DEN with a stop in OAK so could fly to DEN early morning and then on to HNL.
If you want to make use of it from the East Coast, you're going to need a positioning flight or be ok with spending a day or two in the Bay Area - which could be a fun trip nonetheless... it just depends on how much time you have.