Cron Parser
Parse and explain cron expressions.
At minute 0 at hour 0 every day every month every day of the week
┌───────────── minute (0-59)
│ ┌──────────── hour (0-23)
│ │ ┌───────── day of month (1-31)
│ │ │ ┌─────── month (1-12)
│ │ │ │ ┌────── day of week (0-6)
│ │ │ │ │