Cron Expression Syntax & Structure

A comprehensive guide to understanding Cron syntax, field order, range limitations, and platform dialect variations.

Field Positions in 5, 6, and 7-Field Dialects

Dialect	Field Count	Field Sequence
Linux / POSIX Crontab	5 Fields	Minute Hour DOM Month DOW
Spring Boot (@Scheduled)	6 Fields	Second Minute Hour DOM Month DOW
Quartz Scheduler	6 - 7 Fields	Second Minute Hour DOM Month DOW [Year]
AWS EventBridge	6 Fields	Minute Hour DOM Month DOW Year

Day-of-Month vs. Day-of-Week Union Rule

In standard Linux Cron, if both Day-of-Month (DOM) and Day-of-Week (DOW) are specified (i.e. neither is a wildcard *), the command executes when either the day of the month or the day of the week matches (logical OR / union).

For example, 0 0 1,15 * 1 will trigger on the 1st of the month, the 15th of the month, and on every single Monday throughout the month.