Why does */15 always align to :00, :15, :30, :45?

Step values in cron are computed from the field's minimum (0), not from an arbitrary starting point — so */15 in the minute field always expands to 0, 15, 30, 45 regardless of when the schedule was created.

Is every 15 minutes a good interval for a cron-based CI job?

It's reasonable for lightweight checks (linting, smoke tests) but most teams trigger CI on push/PR events instead of polling on a timer, reserving cron schedules for nightly or periodic jobs that aren't tied to code changes.

How do I run every 15 minutes only on weekdays?

Add a day-of-week restriction: */15 * * * 1-5 keeps the quarter-hour cadence but only fires Monday through Friday.

Cron: Every 15 Minutes

*/15 * * * * runs on the quarter hour — :00, :15, :30, :45 — four times per hour. It aligns naturally with how most people think about time in chunks, which makes it a popular choice for reports, digest emails, and moderate-frequency background jobs.

*/15 * * * *

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Examples & Variations

*/15 * * * *

Every 15 minutes

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*/15 6-22 * * *

Every 15 minutes, 6 AM–10 PM

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0,15,30,45 * * * 1-5

Every 15 minutes, weekdays only

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Common Mistakes

Expecting */15 to run relative to deploy time — it always aligns to :00/:15/:30/:45 of the clock, not to whenever the crontab entry was written.
Choosing 15 minutes as an arbitrary default without checking whether your users actually need data that fresh — longer intervals often work fine and cost less.
Not handling daylight saving time transitions on systems where cron runs in local time — a 15-minute job can run twice or not at all during a clock change, depending on server configuration.

Best Practices

For anything downstream of an external API, 15-minute polling is usually gentle enough to avoid rate-limit issues while staying reasonably fresh.
If DST matters to your job, run your cron daemon in UTC and convert for display, avoiding the twice-a-year ambiguity of local time transitions.
Combine with an hour range to avoid unnecessary overnight runs if the job only serves daytime traffic.

Frequently Asked Questions

Why does */15 always align to :00, :15, :30, :45?: Step values in cron are computed from the field's minimum (0), not from an arbitrary starting point — so */15 in the minute field always expands to 0, 15, 30, 45 regardless of when the schedule was created.
Is every 15 minutes a good interval for a cron-based CI job?: It's reasonable for lightweight checks (linting, smoke tests) but most teams trigger CI on push/PR events instead of polling on a timer, reserving cron schedules for nightly or periodic jobs that aren't tied to code changes.
How do I run every 15 minutes only on weekdays?: Add a day-of-week restriction: */15 * * * 1-5 keeps the quarter-hour cadence but only fires Monday through Friday.

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Cron: Every 10 Minutes

Schedule a cron job every 10 minutes with */10 * * * *. See variations, common mistakes, and when 10-minute polling makes sense.

Cron: Every 30 Minutes

Run a cron job every 30 minutes with */30 * * * *. See half-hourly scheduling examples, common mistakes, and best practices.

Cron: Every Hour

The cron expression for every hour is 0 * * * *. See hourly scheduling examples, common mistakes, and best practices for cron jobs.