It sounds like you're wanting to get returned to you everything that is not otherwise captured in a capture group. There is no regex functionality to do that.

What is the problem you're trying to solve? If you go and match

pattern = r"Date: (\d{4})-(\d{2})-(\d{2})"

then what are you going to do with the results?

leftovers = ["Date: ", "-", "-", ""]