Cron Expression Generator & Next Run Calculator

About this cron expression

A traditional crontab schedule has five time fields followed by a command. This page works with only the five-field schedule: minute, hour, day of month, month and day of week.

The parser follows POSIX day matching: when both day-of-month and day-of-week are restricted, a date matches when either field matches. It also supports common Unix extensions for slash steps, English month or weekday names and Sunday as 7.

Cron expressions control scheduled tasks across servers, CI/CD pipelines, and automated jobs. Yet the five-field syntax is notoriously error-prone: off-by-one mistakes, misunderstood field ranges, and daylight-saving surprises crash in production. This free cron expression generator turns natural language intent into valid cron syntax and calculates upcoming runs so you see exactly when jobs will execute.

Generate expressions from presets (hourly, daily, weekdays) or build custom schedules using minute, hour, day of month, month, and day of week fields. The validator explains what each field means in plain English, catches common mistakes, and supports POSIX extensions like slash-separated steps and English weekday names. Calculate the next 10, 50, or custom number of run times in your local timezone or UTC—essential before deploying production schedules.

Real-world edge cases trip up many schedulers: daylight-saving transitions, the interaction between day-of-month and day-of-week when both are specified, and dialect differences across cron implementations. This tool follows POSIX standards and documents where extensions apply, helping you verify behavior matches your target scheduler. Test your expression against real dates, see the exact run times before they happen, and catch problems during development rather than in production.

How to use this tool

1. 01

   Enter all five fields

   Use an asterisk for every value, a comma for lists, a hyphen for inclusive ranges and a slash after an asterisk or range for the supported step extension.

2. 02

   Choose how to display time

   Calculate in the current browser timezone or UTC. The start field itself is entered as browser-local wall time.

3. 03

   Verify on the target system

   Compare the generated schedule with your cron implementation before deploying because extensions and daylight-saving behavior vary.

Worked examples

0 9 * * MON-FRI

Minute 0, hour 9, every day of month and month, Monday through Friday

*/15 9-17 * * MON-FRI

09:00, 09:15, 09:30 … 17:45 on weekdays

Limits and edge cases

• This is a five-field Unix-style dialect. Quartz tokens ?, L, W and #, a seconds or year field, @daily aliases and commands are not accepted.
• Slash steps, names such as MON and Sunday 7 are common extensions and are not part of the smallest portable POSIX grammar.
• If neither day field contains an asterisk, day-of-month and day-of-week use OR matching: 0 9 1 * MON runs on the first and on Mondays. If either contains an asterisk expression such as */2, both expanded sets must match, following common Cronie behavior.
• Daylight-saving transitions can skip or repeat local wall times, and cron implementations differ. UTC schedules avoid DST but may not match a desired local clock time all year.

Standards and references

• POSIX.1-2024 — crontab utility and schedule grammar