Reading cron syntax without a lookup table

A standard cron expression has five fields, always in the same order: minute, hour, day-of-month, month, day-of-week. The trick to reading one quickly is remembering that order goes from smallest unit of time to largest, then day-of-week gets tacked on at the end as an alternate way to specify days.

0 9 * * 1-5 reads as: minute 0, hour 9, any day of month, any month, weekdays 1 through 5 (Monday–Friday). In plain English: 9:00 AM, Monday through Friday.

The symbols worth knowing: * means "every value" for that field. A comma (1,15) means a list of specific values. A hyphen (1-5) means an inclusive range. A slash (*/15) means "every N units" — */15 in the minute field means every 15 minutes.

One genuinely confusing part: if both day-of-month and day-of-week are specified as something other than *, most cron implementations treat it as OR, not AND — the job runs if either condition is met, not only when both are true. This trips people up constantly and is worth double-checking in your specific scheduler's docs if you're combining both fields.

The other thing cron expressions don't tell you on their own: timezone. The same expression can mean a different wall-clock time depending on how the server or scheduler is configured — worth confirming separately if a job seems to run at an unexpected hour.

If you'd rather not parse the fields by hand, the cron explainer turns an expression into a plain-English sentence automatically.