Free tool · runs in your browser
Cron Expression Explainer
Paste a five-field cron expression or a @daily-style macro to see what it means and when it will actually run.
What the explainer checks
The tool parses each of the five fields into the exact set of values it matches, then evaluates them the way Vixie-style cron does: a job runs when minute, hour and month match, and the two day fields combine with OR when both are restricted. Steps such as */15 are expanded from the lower bound of the field, which is why */2 in day-of-month starts on the 1st.
Next run times are computed minute by minute in this browser's local time zone. That makes daylight-saving behaviour visible: a run scheduled inside a skipped hour simply does not appear on the transition day.
Mistakes the output exposes
Most broken crontabs are field-order errors or dialect errors. A six-field expression is reported rather than silently misread, because Quartz and Spring put seconds first while AWS EventBridge keeps minutes first. A day pair such as 0 0 1 * 1 is described as “the 1st OR every Monday”, which is the point where many schedules surprise their authors.
The explainer does not run jobs and does not contact a server. Use the environment that runs the daemon to confirm time zone and permissions, since those are outside what any expression can show.
Frequently asked questions
Which cron syntax does this tool explain?
The classic five-field Vixie cron syntax with @macros, as used by cronie and Debian cron. Quartz and Spring use different field orders.
Why does my job run on Mondays and on the first of the month?
Both day fields are restricted, and Vixie-style cron combines them with OR. Express an AND condition inside the command instead.
Which time zone are the run times in?
Your browser's local time zone, which is shown with the results. A server often runs in a different zone, frequently UTC.