*/15 * * * * — what this cron expression means
The cron expression */15 * * * * runs every 15 minutes (4 times an hour). Here is the field-by-field breakdown and what it means in plain English.
What */15 * * * * means
It runs every 15 minutes (4 times an hour).
Field by field
minute=*/15 → 0,15,30,45; all other fields *.
The step */15 fires at the top of the hour and at quarter past, half past, and quarter to — four runs every hour, around the clock.
When it runs next
Next runs: the next :00, :15, :30 or :45.
FAQ
What does */15 * * * * mean?
It runs every 15 minutes: at :00, :15, :30 and :45 of every hour, every day.
How do I offset it to :05, :20, :35, :50?
Steps always start at 0. For a 5-minute offset use an explicit list: 5,20,35,50 * * * *.