Feature summary (what you would like to be able to do and where):
FileImporter should date Now Commons tags. This helps with categorization.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
This is currently done by FastilyBot on enwiki, for example https://en.wikipedia.org/w/index.php?title=File:Google_cache_link_for_Wikipedia_main_page.png&diff=next&oldid=1059455829

Benefits (why should this be implemented?):
Small investment to reduce watchlist spam, get files categorized right quicker, free up some bot resources for Fastily and a tiny reduction in database load/size.