Getting started with Job.apex
Job Management
We can create a job like this:
Job j = new Job('test', new CustomJob()).everyDay().atHour(8);
Jobs.getInstance().schedule(j);
Or we can unschedule it:
Jobs.getInstance().unschedule('test');
Or reschedule it.
j.atHour(10);
Jobs.getInstance().reschedule(j);