Star Trek: Enterprise

Horizon - S2-E20

Corrected entry: In "Horizon" they talk about going to visit a system to watch a geological event that will take place in a week from then. Mayweather says that this system is 30 lightyears away from them. By using the Warp speed calculator you see that this trip would take about 51 days. Warp 5 is too slow to get there in time, but still they arrive in time.

Correction: In Star Trek, warp speed has never been precisely defined. Since when is a fansite considered canon, especially for things like this?