Timing is everything - and that is especially true in applying for a faculty position.
Too often, faculty job candidates wait too long before they start applying for jobs. Faculty searches are a long, drawn-out process and if you wait too long to start searching, you’ll miss part (or all) of the normal hiring cycle.
Filling a faculty position is not an easy task with many rules and regulations that Universities have to abide by to hire a new professor. Given the complexity of the search process, it can take many months to conduct a search and hire a faculty member.
Because of this, many Universities start searches as early as one year before the actual first day of employment, so you should start looking for job advertisements at least one year before you anticipate being ready to start a new job.
If you want to be considered for faculty positions that start in mid-August in 2020, you need to start looking for available jobs in mid-August 2019. That means that you’ll start looking for a job (or post-doc) before you’ve probably done much work on your dissertation!
....if you wait too long to start searching, you’ll miss part (or all) of the normal hiring cycle.