CronDrive

Cron every 4 hours

0 */4 * * *

Change the time zone to see when it runs on your server.

It's 04:09 there now (UTC+00:00).

Which time zone do I choose?

The time zone of the server where the crontab runs, which may not be yours. To see it, run this on the server:

timedatectl | grep "Time zone"

If the crontab sets CRON_TZ, choose that one.

Every 4 hours

0 minute
*/4 hour
* day
* month
* weekday

Next runs (UTC)

  1. Sat 17 Oct, 08:00
  2. Sat 17 Oct, 12:00
  3. Sat 17 Oct, 16:00
  4. Sat 17 Oct, 20:00
  5. Sun 18 Oct, 00:00
  6. Sun 18 Oct, 04:00
  7. Sun 18 Oct, 08:00
  8. Sun 18 Oct, 12:00
  9. Sun 18 Oct, 16:00
  10. Sun 18 Oct, 20:00

Know when it doesn't run

CronDrive emails you, or posts to Slack, when a job with this schedule fails, or doesn't start or finish on time. Free for up to 15 jobs.

What you'd see with this schedule

An example with the last runs of this schedule and made-up results: one failed and one didn't run.

Times in UTC.

Due
Saturday 17 October 2026
00:00 On time Started 00:00, finished 00:13, took 13 min.
Friday 16 October 2026
20:00 Didn't run Alerts sent at 20:05 and 20:30.
16:00 On time Started 16:00, finished 16:14, took 14 min.
12:00 Failed with code 1 Alert sent at 12:04. Started 12:00, finished 12:04, took 4 min.
08:00 On time Started 08:00, finished 08:13, took 13 min.
04:00 On time Started 04:00, finished 04:14, took 14 min.

The alert of the failed run

Email from CronDrive, Fri 16 Oct, 12:04

Failed (exit code 1): "Your job"

The job "Your job" failed with exit code 1.

If you connect Slack, the same message goes to your channel.

The change in your crontab

0 */4 * * * curl -fsS -m 10 https://job.crondrive.com/uG2Exw/start/$$; /path/to/job.sh; curl -fsS -m 10 https://job.crondrive.com/uG2Exw/end/$?/$$

Two calls around your command, in the same line. Your job's line comes with its own token.

Monitor this schedule

Format

Cron is driven by a crontab (cron table) file, a configuration file that specifies shell commands to run periodically on a given schedule. On Linux you can run crontab -e to edit it.

Each line has a cron expression made of five fields, followed by a shell command to execute. A * means every value; 1,5 is a list, 1-5 a range and */5 a step.

* minute 0-59
* hour 0-23
* day 1-31
* month 1-12
* weekday 0-6, Sunday is 0

Examples

Expression Description
* * * * * Every minute
*/2 * * * * Every 2 minutes
*/3 * * * * Every 3 minutes
*/5 * * * * Every 5 minutes
*/10 * * * * Every 10 minutes
*/15 * * * * Every 15 minutes
*/20 * * * * Every 20 minutes
*/30 * * * * Every 30 minutes
0 * * * * Every hour
0 * * * 1-5 Every hour on Monday through Friday
0 */2 * * * Every 2 hours
0 */3 * * * Every 3 hours
0 */4 * * * Every 4 hours
0 */6 * * * Every 6 hours
0 */8 * * * Every 8 hours
0 */12 * * * Every 12 hours
0 0 * * * Every day at 00:00
0 8 * * 1-5 At 08:00 on Monday through Friday
0 0 * * 1 At 00:00 on Monday
0 0 * * 0 At 00:00 on Sunday
0 0 1 * * At 00:00 on day 1 of the month
1,5 * * * * At minutes 1 and 5 of every hour
1-5 * * * * At minutes 1 through 5 of every hour
0 2 * * * Every day at 02:00
0 1 * * 1,2 At 01:00 on Monday and Tuesday
30 9-17 * * 1-5 Every hour from 09:30 to 17:30 on Monday through Friday
0 0 */5 * * At 00:00 every 5 days