How to read a five-field cron expression in English
Paste minute hour day month weekday and get a plain-language summary — the reverse of Cron Builder, still UNIX-style, still local.
Explainer vs builder
Cron Explainer at /tools/cron-explainer expects exactly five whitespace-separated fields: minute, hour, day of month, month, weekday. It prints English such as “every 15 minutes from 09:00 through 17:00 on Monday–Friday.” Cron Builder at /tools/cron-builder is the opposite: dropdowns and presets (for example weekdays at 9 AM) write the string and show next run times. Use the explainer when a colleague pasted 0 9 * * 1-5 into chat. Use the builder when you are composing from scratch.
Steps
1) Open Cron Explainer. 2) Paste a five-field expression (example: */15 9-17 * * 1-5). 3) Read the explanation. 4) If you need next-run estimates or field editors, switch to Cron Builder. Seconds (six-field cron) and systemd OnCalendar are rejected or misread — this page is UNIX crontab style. A ? on a day field is treated like * on the builder; keep expressions conventional.
Worked example
0 9 * * 1-5 is 09:00 on weekdays. 0 0 1 * * is midnight on the first of the month. */5 * * * * is every five minutes. GitHub Actions weekday numbering can differ from cron’s 0–7 Sunday convention — confirm against the runner. Timezone is the system that executes the job, not this browser, unless you documented UTC.
Limits
No Quartz “year” field. No AWS EventBridge cron extras. Ranges and steps follow common UNIX rules the explainer implements; exotic combinations may need the man page for your cron daemon. Next-run tables live on the builder page.
Related time tools
Timestamp Converter for Unix instants. Time Zone Converter for wall clocks. Timer and Pomodoro for human focus, not schedulers. Nothing here submits a crontab to a server.
Privacy
Expressions stay in the browser. Related: /tools/cron-builder, /tools/timestamp-converter. Close the tab if the schedule implies internal batch names you should not leave on screen.