12/12 lighting issue

hey guys this is my second week of flower i had my plant from 6pm to 6am everyday but do to some unfortunate events i had to switch it up to 10am to 10pm my question is how would i switch it back to the original time and i know this might cause the plant stress but how bad would it be to do?

yes it's get stress,If You change time for 1-4h it's ok,but if You change it for 8h it's bad.
Use timers. It's cost in eBay 5-8 $

If not sure how much stress is caused, but to minimize it try to change the schedule in small increments of an hour or so like SilvaDuss says. I've also read that you want to extend the dark time when changing your schedule (make sure that they get at least 12 hours of darkness).