Ok, I need an Almanac for sunrise and sunset

[nattydread]

Im heading to intercept a convoy and its nighttime. I need to know when I can expect to have some light in order to attack these guys. I'd like to attack during the point where its still dark, but their is enough light creeping over the horizon to allow for better visibilty...what is that dusk, morning twilight? Anyway you know what I mean!