Sorry for my very poor english
I can’t believe that in bbpress forum there is no such a fundamental thing as post and topic date! I thing 80% of forum users need exact post date, not its freshness.
I spend a lot of time on this issue and finally fixed it!
All you need is to use both “Accurate Post Time” AND “User Timezones” plugins. First is for showing date and second is for setting it correctly.
It works fine for me!