Cron Expression Explainer & Schedule Visualizer

Translate standard 5-field Unix crontab expressions into plain English sentences. Visualize future scheduled execution dates with interval breakdown.

Cron Expression

Schedule Presets
Plain English Translation
Runs every 15 minutes.

Min

*/15

Hour

*

DOM

*

Month

*

DOW

*

Upcoming Execution Timestamps (UTC)
Run #1Thu, 10 Sep 2026 19:34:57 UTC
Run #2Fri, 11 Sep 2026 19:34:57 UTC
Run #3Sat, 12 Sep 2026 19:34:57 UTC
Run #4Sun, 13 Sep 2026 19:34:57 UTC
Run #5Mon, 14 Sep 2026 19:34:57 UTC
Run #6Tue, 15 Sep 2026 19:34:57 UTC

POSIX / Vixie Crontab Compatible

Fully compliant with standard Linux/Unix crontab daemons, GitHub Actions workflows, AWS EventBridge, and Kubernetes CronJobs.

Temporal Set Theory & POSIX Cron Execution Formulations

Cron scheduling daemons evaluate predicate constraints over discrete timestamps:

1. Cron Timestamp Predicate Evaluation Equation
T_{exec} = { t \in \text{Time} \mid t_{min} \in M \land t_{hr} \in H \land (t_{dom} \in D_{dom} \lor t_{dow} \in D_{dow}) \land t_{mo} \in \text{Mo} }
2. Step-Interval Modulo Formula
k \in [0, N-1] \iff (k \pmod s) = 0
Step-by-Step Cron Expression Evaluation Breakdown
Step 1: 5-Field Lexical Tokenization
Split string into [Minute, Hour, DOM, Month, DOW] tokens.
Step 2: Step & Range Expansion
Expand */15 to {0, 15, 30, 45} and 1-5 to Mon through Fri.
Step 3: Natural Language Synthesis
Translation=Unambiguous Human-Readable Schedule

Cron Field Index & Special Characters Reference

FieldAllowed RangeSpecial CharactersExample Meaning
1. Minute0 – 59* , - /*/10 = Every 10 minutes
2. Hour0 – 23* , - /9-17 = Working hours
3. Day of Month1 – 31* , - / ? L1,15 = Bi-monthly payroll
4. Month1 – 12 or JAN-DEC* , - /*/3 = Quarterly
5. Day of Week0 – 6 (0=Sun)* , - / ?1-5 = Mon through Fri

Frequently Asked Questions

What are the 5 fields of a standard Unix crontab expression?
A standard Unix crontab contains 5 whitespace-separated fields: 1. Minute (0–59), 2. Hour (0–23), 3. Day of Month (1–31), 4. Month (1–12 or JAN–DEC), and 5. Day of Week (0–6 or SUN–SAT, where 0 and 7 both represent Sunday).
What does */5 or */15 mean in a cron expression?
The forward slash (/) defines step/interval values. When placed after an asterisk (`*/N`), it specifies periodic repetitions. For example, `*/5 * * * *` in the minute field means 'every 5 minutes'.
How does cron handle Day of Month and Day of Week simultaneously?
In standard POSIX crontab engines, if both Day of Month (DOM) and Day of Week (DOW) are specified with non-asterisk values, cron evaluates them as a union (OR) condition. The command will trigger if either condition evaluates to true.
How do timezone differences affect cloud cron jobs?
Cloud services like GitHub Actions, AWS EventBridge, and Vercel Cron execute all cron schedules in UTC. If you want a task to run at 9:00 AM Eastern Time (UTC-5), you must specify `0 14 * * *` (14:00 UTC).

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