Free tool
Cron Expression Generator and Parser
Read a cron expression in plain English and see exactly when it will next run.
Paste a cron expression to have each field explained and to see the next ten times it will actually fire. Type a schedule you are unsure about and the description updates as you go, which is faster than deploying it and waiting to find out.
The five fields are minute, hour, day of month, month and day of week, in that order. Each accepts a wildcard, a single value, a list like 1,15, a range like 9-17, or a step like */15. The trap almost everyone hits is the last two fields: when both day of month and day of week are restricted, cron runs the job when EITHER matches, not both. So 0 0 13 * 5 is not "Friday the 13th", it is every 13th and every Friday. This tool warns you when an expression is in that state.
How to use it
- Pick a preset, or type your own five-field expression.
- Read the plain-English description and check it says what you intended.
- Look at the next ten run times to confirm the real behaviour.
- Copy the expression once it does what you want.
Frequently asked questions
What do the five fields mean?
In order: minute (0-59), hour (0-23), day of month (1-31), month (1-12) and day of week (0-6, where 0 is Sunday). Month and day names such as JAN and MON are also accepted.
Why does my job run more often than I expect?
Most likely the day-of-month and day-of-week rule. If both fields are restricted, cron treats them as OR rather than AND, so the job fires on either condition. Leave one of the two as a wildcard whenever you mean AND.
What does */15 mean, and is it the same as 0,15,30,45?
In the minute field, yes: both fire at :00, :15, :30 and :45. A step applies from the start of the field range, so */15 in the hour field means 0, 3, 6, 9, 12, 15, 18 and 21, counting from hour 0 rather than from now.
Which timezone does cron use?
Whatever the machine or the scheduler is configured with, which is often UTC on a server and local time on a laptop. The next-run times here are shown in your own timezone, so compare carefully before trusting them for a remote box.
Does this support seconds or non-standard fields?
No. It handles the standard five-field crontab format. Six-field variants that add seconds, and extensions such as @reboot, L or W, belong to particular schedulers rather than cron itself.
The desktop version
Cron Expression Generator in Toolbelt
This page does the job in a browser tab. Toolbelt is the same tool as a native Mac app, plus the things a web page cannot do.
Tools
{
"name": "Holizmi",
"tools": [
"json",
"jwt",
"base64"
],
"live": true
}{
"sub": "12345",
"name": "Henry",
"exp": 1767225600
}019bd4e2-7a10-7c3e-9f21-4a6b8d3e5c07
019bd4e2-7a11-7b8a-8e44-1c2f9a7d6b13
019bd4e2-7a12-7d5f-b0c9-7e3a1f8c2d95 1 1 one
2 2 two
3 + inserted
3 4 three- Check a crontab file in place instead of pasting line by line
- Explain every schedule in a file at once
- Convert next-run times into your own timezone
- Works with no connection, on a server you have only SSH into