SoloDiff

Crontab Generator: Build and Explain Cron Expressions

Build a Unix five-field schedule (minute hour day-of-month month day-of-week), paste an existing line, and read the next sample instants in this browser’s local zone and in UTC. Nothing is sent or stored. This is not a crontab file editor: commands, environment assignments, and leap seconds are out of scope.

Choose a preset or edit the five fields. Next-run samples use the browser clock, not a cron daemon.

Expression

Paste a user crontab schedule, optional trailing command (ignored), or @hourly / @daily / @weekly / @monthly / @yearly. Quartz, EventBridge, and @reboot are called out instead of silently rewritten.

Presets

Fields

Each field is a POSIX list of values or inclusive ranges. * means the field’s full range. */n and a-b/n are Vixie/cronie steps, not POSIX. Names are the first three letters of the English month or weekday.

Explanation

Field Token Matches

Next-run examples

Sample

Samples start at the next whole minute on this device. They assume a daemon that wakes once per minute, POSIX-style 60-second minutes, and no leap seconds. Host cron often uses the daemon’s timezone, not the browser’s.

Local

    UTC

      Limits and dialect notes

      • POSIX crontab is five integer fields plus a command: minute 0–59, hour 0–23, day-of-month 1–31, month 1–12, day-of-week 0–6 (Sunday = 0). Lists and hyphen ranges are standard; steps, names, 7 for Sunday, and @ nicknames are extensions.
      • Vixie, cronie, Debian cron, FreeBSD, and OpenBSD fire when minute, hour, and month match, and when at least one restricted day field matches. If both day-of-month and day-of-week are restricted, the usual rule is a union (either may match). Debian documents a first-character * quirk, so 0 0 */2 * sun can AND the fields there while POSIX would OR them.
      • cronie notes that missing daylight-saving hours never match and repeated hours can match twice. This page increments local wall minutes with the browser Date object and does not model leap seconds.
      • Kubernetes CronJob uses the same five fields (day-of-week 0–6; 7 is rejected) and treats ? as *. Amazon EventBridge uses six fields and requires ? in one day column. Quartz adds seconds and last/nth tokens. Those dialects are rejected here.
      • OpenBSD and cronie ~ random ranges, FreeBSD @every_second / @N second intervals, @reboot, CRON_TZ, and system-crontab user columns are not scheduled on this page.