Scheduler module- How is the check for publishing done?
It is executed by the cron. The cron triggers a query to check wether something should be published.
It is a bit contraintuitive though. If your cron runs every hour and you want something published on 22:35 and it is past that time it will be actually published the next time your cron runs. So if your cron runs at 22:30 and 23:30 the publish will be at 23:30.