It's widely known that many events of the Dragon Ball movies contradicted the series, sometimes irreconcilably, and that they are "non canon", but does this mean they didn't happen at all? The last two Dragon Ball movies showed many of the events of those movies actually happened in the series. Not long ago, I read an interview in Spanish from someone from the cast of Dragon Ball. I can't remember if it was an animator or director of the last movies, but when talking about the movies and Dragon Ball Super, he said something in the lines of, the true story of Bills, Super Saiyan God, etc, is somewhere in the middle of the movies and the series, meaning the series' events aren't even over the movies. What about former movies such as Super Android 13, Cooler's movies, Broly's movies, etc? Did the events of those movies (those which aren't contradicted irreconcilably) actually happened to some extent in the series' story?
Besides the dragonball super movies everything else in Z is considered non cannon as in it had nothing to do with the actual series. I don't think toriyama was involved in any of the Z movies so they are kind of fanfiction by other authors.
An easy rule to follow is anything that did not happened in the manga is not considered to be a part of the series. If you take the a look a latest super manga you will see similarities with the last two movies so they are considered to be cannon.
They didn't happen in the comic or in the tv show, but the times that each movie's events occurred in can be placed somewhere in the show...Such as Vegetta/Goku/Gogeta vs Janemba, occurs after Vegetta dies, and while Goku is dead. Since Goku was on the Supreme Kai's planet at this time, then the movie is just an alternate version of what's going on.
All the movies before Super, other than the Garlic JR.(even gets his own saga!) one, where just extra story for entertainment.