Groundhog-Day type idea
I was curious if this idea has been done yet...
There are many films in the Groundhog Day genre, but has there ever been one where, every time the day repeats, it is the same day but further into the future? The way we would know is the technology changes, so if it started in the 1960s, by today, there would be social media as opposed to postcards and letter-writing.