Movies that slip and slide between eras tend to do so with a sense of fun or camp. And creating historically accurate costumes and sets is less of an issue if a sense of whimsy is the guiding aesthetic. A sense of whimsy is not the guiding aesthetic for the Sullivan family. John can tell Frank what happened and how to prevent it. Doing so, however, will then have repercussions.
History changes in ways that they don t expect.
Once they have initiated this process, they have to continue. In the first iteration of history that they inadvertently create, there is a second family tragedy. John and Frank then try to fix that, and the process continues. It s a respectable tactic to keep the plot moving, and it has the added advantage of being able to throw the audience numerous curves. This is one movie that kept me guessing right to the end.