Cron Expression Explainer

Decode cron schedules into plain English. Enter a five-field cron expression and see exactly when it fires, with a reference table of the patterns you'll reach for most.

Cron expressionminute hour day-of-month month day-of-week

Explain

Result

How to use this calculator

1. Enter a five-field cron expression: minute, hour, day-of-month, month, day-of-week.
2. Press Explain for a plain-English reading and a field-by-field breakdown.
3. Use * for "every", ranges like 1-5, lists like 1,3,5, or steps like */15.

Formula used

Fields range: minute 0–59, hour 0–23, day-of-month 1–31, month 1–12, day-of-week 0–6 (Sunday=0). An asterisk means "every". A gotcha: setting both day-of-month and day-of-week makes the job run when either matches, not both.

Example calculation

Reading cron without the guesswork

Cron is the Unix scheduler behind backups, reports, cleanups and countless automated tasks — but its terse five-field syntax is famously easy to misread, and a wrong expression silently runs at the wrong time (or never). Translating to plain English before deploying catches those mistakes.

The classic trap: when you specify both a day-of-month and a day-of-week, cron runs the job whenever either matches — so 0 0 13 * 5 fires on the 13th AND every Friday, not only Friday the 13th. Steps (*/15), ranges (9-17) and lists (1,3,5) combine to express almost any schedule once the fields are clear.

Why use this calculator?

• Verify a cron expression means what you intended before deploying it.
• Learn the syntax through the field-by-field breakdown.
• Avoid the day-of-month/day-of-week OR-logic trap.

Frequently asked questions

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