The position needs to be approved by all the administrators before posted. Research schools start posting their positions in early September for the next academic year and the number of open positions reaches its peak in October and November. In smaller schools or for teaching positions, positions are posted sometimes as late as May or June. But your best bet is to have your application ready by August so you don’t miss any opportunities.
As there is a hire freeze and no activity in many universities due to COVID-19 virus. I suspect a lot of position opens up after this goes away.
This social distancing practice is the best time to work from home and work on your teaching and research statements, so when positions pop up, you are ready to apply and ahead of the rest of applicants.