How to Use Cron Syntax in Jenkins for Scheduling Jobs

In Jenkins, use cron syntax in the 'Build Triggers' section under 'Schedule' to run jobs at specific times. The syntax has five fields: minute, hour, day of month, month, and day of week, separated by spaces. For example, H 12 * * 1-5 runs a job at a random minute during 12 PM on weekdays.

Syntax

The Jenkins cron syntax uses five fields separated by spaces:

• Minute (0-59)
• Hour (0-23)
• Day of Month (1-31)
• Month (1-12)
• Day of Week (0-7, where both 0 and 7 mean Sunday)

Each field can be a single number, a range (e.g., 1-5), a list (e.g., 1,3,5), or a special character like * for any value. Jenkins also supports H to distribute load by hashing job names to a consistent time.

plaintext

MIN HOUR DOM MON DOW
0 12 * * 1-5

Example

This example schedules a Jenkins job to run every weekday at 12 PM at a hashed minute to spread load:

plaintext

H 12 * * 1-5

Output

Job runs once every weekday at 12:XX PM, where XX is a consistent hashed minute between 0 and 59.

Common Pitfalls

Common mistakes when using cron syntax in Jenkins include:

• Using six fields instead of five (Jenkins uses five fields only).
• Confusing day of month and day of week fields; if both are restricted, the job runs when either matches.
• Not using H to avoid all jobs running at the same time, which can overload the server.
• Using 0 0 * * * expecting it to run at midnight UTC, but Jenkins uses the server's local time.

Wrong: 0 0 * * * * (six fields, invalid)

Right: 0 0 * * * (runs daily at midnight)

plaintext

Wrong: 0 0 * * * *
Right: 0 0 * * *

Quick Reference

Field	Allowed Values	Description
Minute	0-59	Minute of the hour
Hour	0-23	Hour of the day
Day of Month	1-31	Day of the month
Month	1-12	Month of the year
Day of Week	0-7	Day of the week (0 or 7 = Sunday)

Key Takeaways

Jenkins cron syntax uses five fields: minute, hour, day of month, month, and day of week.

Use H to spread job start times and reduce server load spikes.

Avoid six-field cron expressions; Jenkins only supports five fields.

If both day of month and day of week are restricted, the job runs when either matches.

Jenkins schedules jobs based on the server's local time, not UTC.