Build cron schedules and understand them in plain English.
* * * * *
*/5 * * * *
0 * * * *
0 0 * * *
0 12 * * *
0 0 * * 0
0 9-17 * * 1-5
0 0 1 * *
0 0 1 */3 *
0 0 1 1 *
