You gain time when you travel east to west.

However, if you cross the International Date Line while traveling east to west, you lose a day.

My English major brain is trying to figure out if you just keep circumnavigating Earth westward, can you literally lose a year off your life?

By only traveling westward, you regain time you lost crossing the International Date Line before crossing it again, but you need to change planes at some point.

My flight from California to Australia was 14:35 plus one day.

My flight from Australia to California was 13:20 minus one day.

I didn't regain all the time I lost, right?

So if I just keep traveling back and forth between California and Australia, can I offset my birthdate by one day? Like, my birthday is October 6, but the time I have been alive only adds up to October 5.