How to plan for change to log backup schedule? I've looked everywhere but can't find an answer for this. I know it's an easy question, but I want to be sure I don't screw anything up.

I want to change our log backup from every 30 minutes to every 15 minutes. Our logs are growing too fast.

If I change to every 15 minutes, do I have to set a new start time? Currently is showing to start at 12:00 and end at 11:59.

If I change at 10:00 am, will the existing jobs still run until 12:00? or will nothing run until the new start time is hit?

So for example, if I set a new job at 10:00am, would I also need to change the start time to 10:00am?
If I change to every 15 minutes, do I have to set a new start time? 


Nope! The start and end time is when the schedule is active. So, assuming you still want to take t-log backups every 15 minutes all day, then you just need to adjust that value and the when the next hour/half hour occurs it will take the backup.


  So for example, if I set a new job at 10:00am, would I also need to change the start time to 10:00am?


No - because 10AM is still between 12:00AM and 11:59PM, so the schedule will still be active.