Cron Expression Generator

What are the five fields and their allowed values?

In order: minute (0-59), hour (0-23), day of month (1-31), month (1-12 or JAN-DEC) and day of week (0-7 or SUN-SAT, where both 0 and 7 mean Sunday). Values outside these ranges, and backwards ranges such as 20-10, are reported as invalid with the field named.

What happens when both day-of-month and day-of-week are set?

In classic cron the job runs when either field matches, not both. "0 0 13 * 5" fires at midnight on every 13th and also on every Friday, not only on Friday the 13th. The description the tool writes says so. Some other schedulers combine the fields differently, so check yours.

Why does */7 in the minute field not run every 7 minutes?

A step counts from the start of the field’s range each time. */7 means minutes 0, 7, 14 … 56 and then restarts at 0 in the next hour, leaving a gap of 4 minutes. Steps that divide evenly into 60, such as */5, */10, */15 and */30, give a steady rhythm; the tool points this out for the others.

Which time zone does the expression use?

The expression has no time zone; the scheduler that runs it decides. A classic crontab uses the server’s local time, GitHub Actions schedules use UTC, and other platforms vary. Convert to the scheduler’s zone before writing the hour. Daylight-saving changes can skip or repeat a run scheduled in the hour that is missing or doubled, and this differs between implementations.

Why is my 6- or 7-field expression rejected?

This tool reads the 5-field format only. Quartz and Spring add a leading seconds field, and AWS EventBridge uses six fields with a year and requires a question mark in either the day-of-month or day-of-week position. Those extras, along with the L, W, # and ? characters, are rejected here and should be written for the target system by hand.

Are @daily and @reboot supported?

Yes, in the form common to crontab implementations: @hourly, @daily (or @midnight), @weekly, @monthly and @yearly (or @annually) are expanded to their five-field equivalents, and @reboot is described as a run at daemon start-up. Not every platform that accepts five fields accepts these shortcuts.

Does the tool show the next run times?

No. It validates the syntax, labels each field and writes a plain-English sentence. It does not know your server’s time zone or today’s date, so it cannot list upcoming runs. It does flag a schedule that can never fire, such as day 31 in February.