Cron Schedule Calculator

Frequently Asked Questions

What do the five cron fields mean?

Standard cron has five fields: minute (0–59), hour (0–23), day-of-month (1–31), month (1–12), and day-of-week (0–6, Sunday = 0). For example, "0 9 * * 1" runs at 09:00 every Monday.

How are the next run times found?

Starting from the current time, the parser advances minute by minute and keeps each timestamp whose fields all match the expression. Listing the next N matches gives the upcoming schedule.

What do *, /, ,, and - mean in a field?

"*" matches every value, "*/5" matches every 5th value (e.g. every 5 minutes), "1,15" matches a list, and "1-5" matches a range. Combined, "0 */2 * * 1-5" runs at the top of every other hour on weekdays.

How do day-of-month and day-of-week interact?

In classic cron, when both day-of-month and day-of-week are restricted (not *), the job runs when either matches - an OR, not an AND. So "0 0 1 * 1" fires on the 1st of the month and on every Monday.

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How This Calculator Works

Cron is the scheduling syntax used by Unix crontabs, CI pipelines, Kubernetes CronJobs, and most serverless schedulers. A standard expression has five space-separated fields - minute, hour, day-of-month, month, and day-of-week - and a job fires whenever the current time matches every field. The syntax is terse, and it is genuinely hard to read "*/15 9-17 * * 1-5" and know instantly when it runs. This calculator parses your expression, validates every field, and then walks forward minute by minute from now to list the next several actual run datetimes in your local timezone. It supports the common operators - * (every value), step */n, ranges 1-5, and lists 1,3,5 - plus the familiar named presets such as @daily and @hourly. Seeing the concrete next-run times is the quickest way to confirm a schedule does what you intend before you commit it.

Formula / Method

Each field is expanded into the explicit set of values it permits within its legal range - minute 0–59, hour 0–23, day-of-month 1–31, month 1–12, day-of-week 0–6 (Sunday = 0). A bare * fills the whole range; a-b fills an inclusive range; a,b,c unions explicit values; and */n (or a-b/n) takes every n-th value. A given minute fires when its minute, hour, day-of-month, month, and day-of-week all belong to their respective sets. To find the next runs we start at the next whole minute, set seconds to zero, and step forward one minute at a time, testing the match condition and collecting datetimes until we have the requested count (capped at 20) or exhaust a one-year search window. The one-year guard means impossible schedules such as February 30 are reported rather than looping forever.

Worked Example

Consider */15 9-17 * * 1-5 - "every 15 minutes, between 9am and 5pm, Monday through Friday." The minute field */15 expands to {0, 15, 30, 45}; the hour field 9-17 to {9, 10, …, 17}; day-of-month and month are unrestricted; and 1-5 is Monday through Friday. So on a typical Tuesday the job runs at 09:00, 09:15, 09:30 … up to 17:45, then nothing until 09:00 Wednesday, and it skips Saturday and Sunday entirely. If you run this on a Friday afternoon the next five runs will be the remaining quarter-hours of that day; run it Friday evening and they roll over to Monday morning. The preset @daily expands to 0 0 * * * - once at midnight every day.

Common Mistakes

Reading the fields in the wrong order - it is minute first, then hour; many people swap them and schedule a job for the wrong time.

Forgetting Sunday can be both 0 and 7 in some implementations - this tool uses 0–6 with Sunday = 0.

Setting both day-of-month and day-of-week - classic cron treats them as an OR, which surprises people; this tool requires both to match (AND).

Using */0 or a zero step - the step must be a positive integer.

Assuming UTC - servers run cron in their own timezone; this tool shows times in your local zone, which may differ from production.

Tips & FAQ

What timezone are these times? Your browser's local timezone - your cron server may run in UTC, so adjust accordingly. Does this support seconds? No - standard 5-field cron has minute resolution; 6-field (seconds) variants like Quartz are not handled here. What about @reboot? That fires on startup, not on a clock, so it has no predictable datetime to list. Why does my job run more often than I expect? A lone * in the minute field means every minute - 1,440 times a day; pin the minute to a value to avoid that. How do day-of-month and day-of-week interact? Vixie cron ORs them when both are restricted; this calculator ANDs them, so verify against your scheduler's docs for edge cases. Can I schedule the last day of the month? Not in pure cron - that needs L from Quartz-style extensions, which standard cron lacks. Use this preview as a sanity check, then test the real schedule in a staging environment before relying on it.

Frequently Asked Questions

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