Create and visualize cron expressions with clear explanations.
Examples: *, */15, 0-30, 0,15,30
Examples: *, 9, 0-12, */2
Examples: *, 1, 1-15, ?
Examples: *, JAN-DEC, 1-6
Examples: *, MON-FRI, 0,7 (Sun)
0 9 * * *