When does this movie take place?

well, since Vegeta is a super saiyan, yet Gohan's still a kid, i would say it takes place rite after trunks tells goku about the androids and leaves, because by then, i think vegeta had already ascended, but didnt tell anybody cuz he wanted to save it as a big surprise or sumthin, becuz remember, only Goku saw vegeta as a super saiyan in this movie, and by the time everybody else saw, Goku already got his ass kicked by #19, so he couldnt say anything, or maybe its just a goof, lol

It's a movie. The movies NEVER take place, they're strictly side-stories for entertainment only that dont fit into the actual series timeline. But, if you want me to give you a time it could have taken place, I'd say it happens in the alternate Future Trunks Timeline. Goku DID kill Frieza in that timeline, therefore it's the most likely possibility.