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Cron Expression Explainer

Paste a cron expression and get a plain English explanation, a field by field breakdown and the next times it would run, in your local timezone or UTC. Reads five field crontab syntax, six fields with seconds, names like MON and macros like @daily.

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Five fields: minute, hour, day of month, month, day of week. A sixth field in front adds seconds, and macros like @daily work too.

Nothing to explain yet
Type a cron expression above, or try one of the examples, to see what it means and when it runs.

Next steps

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About the Cron Expression Explainer Tool

This tool reads a cron expression and tells you what it actually does. Paste something like */5 9-17 * * MON-FRI and you get the schedule in plain English, a breakdown of every field with the matching values highlighted, a live countdown to the next run, and a list of the exact times it would fire next. Everything is color coded by field, from the characters you type to the words in the summary, so you can see at a glance which part of the expression does what.

It understands the classic five field crontab format, six field expressions with a leading seconds field, month and weekday names like JAN and MON, and the shorthand macros @hourly, @daily, @weekly, @monthly and @yearly.

What you can do

  • Turn a cron expression into a plain English sentence.
  • See which minutes, hours, days and months each field matches, at a glance.
  • List the next runs of a cron schedule in your local timezone or in UTC.
  • Watch a live countdown to the next run, ticking every second as runs come and go.
  • Check six field expressions with seconds, as used by Quartz and many schedulers.
  • Expand macros like @daily into their five field form.
  • Spot mistakes, with errors that name the field and value that broke parsing.

How to use the Cron Expression Explainer

  1. 1Type or paste a cron expression, or pick one of the examples.
  2. 2Read the plain English summary and check each field in the breakdown.
  3. 3Look through the upcoming runs to confirm the schedule does what you expect.
  4. 4Switch the run times to UTC if the job runs on a server that uses it.

How a cron expression is built

A classic cron expression has five fields, always in the same order: minute (0 to 59), hour (0 to 23), day of month (1 to 31), month (1 to 12) and day of week (0 to 7, where both 0 and 7 mean Sunday). Each field takes a * for any value, a single number, a list like 1,15,30, a range like 9-17 or a step like */5, and these combine freely. Months and weekdays also accept names, so MON-FRI and JAN,JUL work.

Some schedulers put a sixth field in front for seconds. This tool detects that automatically, so a six field expression just works.

The two day fields follow an OR rule

Day of month and day of week are special. When both are restricted, classic cron fires when either one matches, not both. 0 0 13 * FRI runs every Friday and additionally on the 13th of every month, which surprises a lot of people. The tool warns you when an expression falls into this case, and the upcoming runs show the real effect.

What it does not read

The Quartz extras L, W and # (last day, nearest weekday, nth weekday) are not part of classic cron and are not supported, and neither is @reboot, which has no time schedule to explain. If an expression uses them you get a clear message instead of a wrong explanation.

The upcoming runs are computed in the timezone you pick, your browser's local one or UTC. The machine that actually runs the job decides the real timezone, so check what your server or scheduler uses before trusting wall clock times.

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