I'm running through my backlog of Christmas movies on the DVR and just finished A Timeless Christmas. Agree with all who said he should have figured out a way to get back. Once the adrenaline of new experiences like pizza and television and spending time with Rosie's great-granddaughter wore off, I think 2020 Charles would be filled with regrets that he didn't go home. In 2020 he has to live forever in a future where, unless he gets an under-the-table job somehow, he has to give tours in a house that he knows is rightfully his, and there is a literal park in town memorializing the man that to Charles will forever only be the enemy that stole his milling invention and his fiancée. It would have worked better and made more sense, for me, if Charles used the clock to go back to do some things differently and then somehow returned to 2020 Megan.
I also ended the movie feeling sorry for 1903 Rosie, who inevitably died without ever knowing what happened to Charles Witley.