Dynamo only runs when you tell it to. Running a Revit graph in Automatic mode is almost exclusively a bad idea, so you would have to manually run the graph at the end of every day to capture all the new elements.
Writing the date to a parameter is the easy part. But it’s much more complicated than that:
- Which elements are you concerned with? You’ll have to filter for the categories you want.
- Filtering all these categories in a large model could take a decent amount of time.
- How do you deal with “existing” elements that have to be recreated? How do you deal with people copying elements that already have a date assigned to them?
- The more elements you’re dealing with, the more exceptions you normally have to deal with as well. This can quickly complicate your graph.
- Modifying a large amount of elements all at once has the possibility of “corrupting” local models.
What you’re asking is simple in theory but much more involved than you may realize. There are third-party add-ins that track elements like this that you may want to look into. They will likely be more stable and less intrusive than a Dynamo solution.