My confirmation time is a time earlier than 9am, it started at 10am but people were not telling me they weren't coming and I had guys on standbywho would need to know before 9am to plan their travel or day. Also some bookings are for 9am, 10am, 10.30am so confirm became a time before 9am or 2 hours prior which ever is the earliest.
Main issue is those who forget to confirm and this happens even after paying a significant deposit, I do send the confirm time by text or email when acknowledging receipt of the deposit. So they have it, and explain if I do not receive the confirm I may assume booking is off, deposit lost.