He will send you anywhere, to any time period (past, present or future), for one week.
Where and when will you go? Why?
At the end of the week, you are given the choice: Stay there in that place and time period forever, or return to your regularly scheduled present-day life. If you stay, all your family and friends will know is that you up and disappeared, never to be seen again.
Do you stay?
ETA: Let's simplify this shit. No, you won't fuck anything up anywhere (or anywhen). Yes, you instantly are away of all the languages and cultural knowledge you'd need in order to not get yourself killed.