Since there have been quite a few poisoned-bottle problems posted to the site already, I thought I'd post a general formula to cover all future variations of this problem (at least where a single poisoned bottle is concerned).

You have $n \le (m+1)^k$ bottles of wine, one of which is poisoned. The poisoned wine kills any person who drinks it at the stroke of midnight on the day that they drank it. You have $k$ prisoners to test the wine by making them drink it and possibly killing them, and $m$ days to conduct these death trials. How do you plan out the tests so that you can figure out which bottle is poisoned?