On Youtube there used to be a feature where users could search by oldest. It got removed a couple of years ago iirc. YouTube recently brought it back, but it seems to be only for channels. The "sort by upload date" feature only shows recent uploads, making it hard to find older videos. This is especially frustrating if you like watching relics from the past, which I'm sure a lot of users on here can relate to. (╬▔`^▔)
HOWEVER, I've found a workaround thanks to this StackExchange post.
If you want a step-by-step process, here's my example:
Notice that the majority of the videos are recent and have been watched previously. Like most social media, YouTube is no exception when it comes to trying to be up to date as possible. It personalizes your search results to keep you entertained, basically acting as an algorithm.
When I add the before:2011-11-01, I get non-personalized search results. See how the videos are all from 12, 14, and 15 years ago? This isn't a feature for YT itself, but an update made for the Google Search engine, which luckily happens to also work on YouTube. It works with any date, as long as it's in the format of "yyyy-mm-dd".
Now you can watch all of your old, favorite gems! ^^