I know someone in my program at Hopkins who has completed 3 years postdoc, her fellowship ended in June. But she is still around. Does that mean she is staying for another FULL year? (perhaps on a new fellowship) In other words:

Do postdoc positions, or academic outlets for postdocs, usually start at the beginning of the year (end august)? or perhaps semester? or it could be anytime within the year...?
Thank you