Master control

If your scheduling needs are more complex, you need to be ultra-specific; you might not be able to easily use the Schedule Apex page. Let's say you need a process to run once a quarter or just once a year. Instead of trying to hack together some creative schedule, you can just use a CronTrigger. A CronTrigger represents a scheduled job and is similar to a cron job on UNIX systems. CronTriggers can be set with a very specific expression through the System.schedule() method. You can specify the schedule by seconds, minutes, hours, day of month, month, day of week, and year. There are options for using a range, intervals, and all possible numbers. Basically, if you can think of a schedule, you should be able to write a CronTrigger for it such as follows:

//Scheduling a Schedulable Apex Class
myScheduler cls = new myScheduler();
String cronExpression = '0 59 11 * * ?';  //Nightly at 11:59pm
String jobId = System.schedule('Job Name', cronExpression, cls);