Advanced Cron Syntax: 15 Practical Examples for Every Schedule

Beyond Basic Cron

Once you know the 5-field format, the real challenge is crafting the right expression for your use case. Here are advanced patterns with explanations.

Common Advanced Patterns

Pattern	Expression	When It Runs
Every 15 minutes	`*/15 * * * *`	:00, :15, :30, :45
Every 90 minutes	`0 */90 * * *` (not supported — see below)	—
Every 2 hours	`0 */2 * * *`	Midnight, 2AM, 4AM...
Every 6 hours	`0 */6 * * *`	Midnight, 6AM, Noon, 6PM
Twice daily at specific times	`0 8,20 * * *`	8:00 AM and 8:00 PM
Every weekday at 9:30 AM	`30 9 * * 1-5`	Weekdays only
Every Monday and Thursday	`0 0 * * 1,4`	Midnight Mon & Thu
First day of every month	`0 0 1 * *`	Midnight on the 1st
Every 15th and last day	`0 0 15,L * *`	Midnight 15th and last day
Every quarter (Jan, Apr, Jul, Oct)	`0 0 1 1,4,7,10 *`	First of quarter months

Important: Step Values and Limits

Cron step values like `*/90` for minutes **do not work as expected**. The minute field only supports 0-59. `*/90` would evaluate to `0` (since 90 ≥ 60, it wraps). For intervals longer than 59 minutes, use specific hour/minute combinations:

# Every 90 minutes — not natively possible
# Workaround: use two explicit times
0 0,2,4,6,8,10,12,14,16,18,20,22 * * *
30 1,3,5,7,9,11,13,15,17,19,21,23 * * *

Real-World Examples

Database Backup Every Hour

0 * * * * /usr/bin/pg_dump mydb > /backups/db.sql

Log Rotation at Midnight

0 0 * * * /usr/sbin/logrotate /etc/logrotate.conf

Health Check Every 5 Minutes

*/5 * * * * curl -sS https://example.com/health

Monthly Report on the 1st at 3 AM

0 3 1 * * /opt/scripts/generate-report.sh

Multiple Schedules in One Crontab

# Clean temp files every 6 hours
0 */6 * * * /usr/bin/find /tmp -type f -atime +1 -delete
# Send digest email at 8 AM weekdays
0 8 * * 1-5 /opt/send-digest.sh
# Full system audit on the 1st of every quarter
0 2 1 1,4,7,10 * /opt/audit.sh

Test Your Cron Expressions

Use the Cron Parser tool on YZIF to instantly decode any cron expression. Paste in your pattern and see exactly when it will fire, in both English and Chinese.