Watched at obscure date
The option to mark something as watched without it being marked as watched on that date (and thus not have a date in particular). Maybe it could say "watched previously" and, if needed on the calendar, it could be at the very last, with no date and a heading that says "unknown" or something similar.
This isn’t something we plan to support since many of the site features rely on this data. There are some other support ideas with more background about this request too.
Jake Lockerman commented
This is very important! Please add this feature!