CRON calendar expression for running a task every X minutes

Question

Writing a CRON expression to run every X minute starting at a specific time. The specific time is passed in by a user. My current expression looks like this "0 10/15? * * *" (every 15 minutes)

This runs accordingly every 15 minutes but when the next hour clocks over the next start time is set back to the original minute when set (11:20) instead of clocking over to 11:05. I need it to run every 15 minutes indefinitely from the original start time

This is my first time using CRON and having trouble finding out info on how to write an expression for this correctly.

Answer 1

This expression executes every 15 minutes

0 0/15 * 1/1 * ? *