The new scheduler is based on the cron-utils package and uses the same cron syntax as quartz.
CronScheduler was mainly introduced, because of a ClassLoader leak with the old Quartz implementation.
The leak comes from shiros use of InheriatableThreadLocal in combination with the WorkerThreads of Quartz.
CronScheduler uses a ThreadFactory which clears the Shiro context before a new Thread is created (see CronThreadFactory).
