Cron At Minute 15 and 45 of Every Hour

The cron expression 15,45 * * * * schedules a task to run twice per hour, at the 15-minute and 45-minute marks, every day of the year.

Field-by-field breakdown:

• 15,45 (Minute): At minutes 15 and 45. The list notation specifies two exact trigger points per hour, spaced 30 minutes apart.
• * (Hour): Every hour from 0 through 23. No restriction on which hour the task runs.
• * (Day of Month): Every day from 1 through 31. No restriction on the day of the month.
• * (Month): Every month from January through December. No restriction on which month.
• * (Day of Week): Every day of the week from Sunday through Saturday. No restriction on the day of the week.

This means your task will execute 48 times per day, twice per hour at evenly spaced 30-minute intervals. The key advantage of using minutes 15 and 45 instead of 0 and 30 is offset scheduling. By running at quarter-past and quarter-to the hour, you avoid competing with the majority of cron jobs that run at minute 0 or 30. This is an effective load-balancing technique in environments with many scheduled tasks sharing the same infrastructure. The 30-minute gap between executions gives each run plenty of time to complete. This expression is supported by standard cron on Linux/macOS, as well as cloud services like AWS CloudWatch, Google Cloud Scheduler, and GitHub Actions.