CRON Expression Format
A cron expression represents a set of times, using 6 space-separated fields.
Field name | Mandatory? | Allowed values | Allowed special characters ---------- | ---------- | -------------- | -------------------------- Seconds | Yes | 0-59 | * / , - Minutes | Yes | 0-59 | * / , - Hours | Yes | 0-23 | * / , - Day of month | Yes | 1-31 | * / , - ? Month | Yes | 1-12 or JAN-DEC | * / , - Day of week | Yes | 0-6 or SUN-SAT | * / , - ?
Note: Month and Day-of-week field values are case insensitive. “SUN”, “Sun”, and “sun” are equally accepted.
Asterisk ( * )
The asterisk indicates that the cron expression will match for all values of the field; e.g., using an asterisk in the 5th field (month) would indicate every month.
Slash ( / )
Slashes are used to describe increments of ranges. For example 3-59⁄15 in the 1st field (minutes) would indicate the 3rd minute of the hour and every 15 minutes thereafter. The form “*\/…” is equivalent to the form “first-last/…”, that is, an increment over the largest possible range of the field. The form “N/…” is accepted as meaning “N-MAX/…”, that is, starting at N, use the increment until the end of that specific range. It does not wrap around.
Comma ( , )
Commas are used to separate items of a list. For example, using “MON,WED,FRI” in the 5th field (day of week) would mean Mondays, Wednesdays and Fridays.
Hyphen ( - )
Hyphens are used to define ranges. For example, 9-17 would indicate every hour between 9am and 5pm inclusive.
Question mark ( ? )
Question mark may be used instead of ‘*’ for leaving either day-of-month or day-of-week blank.
You may use one of several pre-defined schedules in place of a cron expression.
Entry | Description | Equivalent To ----- | ----------- | ------------- @yearly (or @annually) | Run once a year, midnight, Jan. 1st | 0 0 0 1 1 * @monthly | Run once a month, midnight, first of month | 0 0 0 1 * * @weekly | Run once a week, midnight on Sunday | 0 0 0 * * 0 @daily (or @midnight) | Run once a day, midnight | 0 0 0 * * * @hourly | Run once an hour, beginning of hour | 0 0 * * * * @minutely | Run once a minute, beginning of minute | 0 * * * * *
You may also schedule a job to execute at fixed intervals. This is supported by formatting the cron spec like this:
where “duration” is a string accepted by time.ParseDuration (http://golang.org/pkg/time/#ParseDuration).
For example, “@every 1h30m10s” would indicate a schedule that activates every 1 hour, 30 minutes, 10 seconds.
Note: The interval does not take the job runtime into account. For example, if a job takes 3 minutes to run, and it is scheduled to run every 5 minutes, it will have only 2 minutes of idle time between each run.
You may also want to schedule a job to be executed once. This is supported by formatting the cron spec like this:
Where “datetime” is a string accepted by time.Parse in RFC3339 format (https://golang.org/pkg/time/#Parse).
For example, “@at 2018-01-02T15:04:00Z” would run the job on the specified date and time assuming UTC timezone.
Dkron is able to schedule jobs in time zones, if you specify the
timezone parameter in a
If the time zone is not specified, the following rules apply:
All interpretation and scheduling is done in the machine’s local time zone (as provided by the Go time package (http://www.golang.org/pkg/time).
Be aware that jobs scheduled during daylight-savings leap-ahead transitions will not be run!
If you specify
timezone the job will be schduled taking into account daylight-savings
and leap-ahead transitions, running the job in the actual time in the specified time zone.