There is a 5 min grace period So Peak is from 635 to 927 And from 1605 to 1857
I phoned TfL to find the answer to this. It’s simple and straightforward:
Peak fares apply from 06:30 to 09:29 and from 16:00 to 18:59 Monday to Friday (excluding public holidays). Off-peak fares apply at all other times. That is, if you touch in during those two three-hour periods, you will be charged the peak fare.
If your journey starts in off-peak time but strays into the peak period, it’s still an off-peak fare.
Credit:stackoverflow.com‘