I have a rather odd fascination with this specific trope, but I think I know why. For those who don't know what I mean, an unintentional period is, as the name states, when a work (be it fiction or non-fiction) dates itself to the period in which it was made, but does so unintentionally. Basically works that are really "in the moment" of then they were made. I think a few reasons why I find this trope interesting are:
-It gives you a look into what things were like at the time the work was made
-You get an idea about what was popular at the time, and might later research what said stuff was
-Similarly, you might also hear jokes that were relevant at the time of the work's making, which can prompt one to research the joke to find out why it was funny at the time
Some major ways a work can unintentionally date itself include: pop culture references, jokes or simply just stories about events or people relevant at the time, making heavy use of media tropes that are all the rage in media at the time, etc.
For some works it can be kinda hard to feel completely timeless, even works looked back on fondly can look dated when you try and think about them in the modern world. For example, in Hey Arnold the character Big Bob runs a "Beeper Emporium." Beepers/pagers haven't been very relevant in a long, being made pretty much obsolete by cell phones that are more affordable and portable than the ones of the 80s and 90s. Similarly there was an episode of King of the Hill dealing with the topic of MySpace and how people like Hank didn't get the appeal of it. Nowadays MySpace is as a social media site is dead and replaced by the likes of Facebook.
So anyway, what are some stuff that you enjoy that nowadays seem dated in some fashion? Here's a few for me:
-Resident Evil 4 (the games references to the War on Terror will only feel relevant to those who grew up during the 00s)
-Grand Theft Auto 3 and 4, and inevitably 5 will be in time (basically any GTA that isn't an actual period piece like Vice City and San Andreas, as GTA3, 4, and 5 all feature very scathing commentary on American culture in the periods in which they were made, arguably even more so with GTA4 as one area that's a major "love it or hate it" area is the games more cynical attitude about a post-George W. Bush America)
-The old Tony Hawk's Pro Skater games (the soundtracks alone let you know when these games were made, usually featuring a lot of ska, stake punk, some rap metal, and the like; they also reflect a period in time when things like The X Games were influencing a lot of American teenagers and kids to try skateboarding)
-An Extremely Goofy Movie (the name alone really reminds me of the period of the 90s when extreme sports and "tude" were all the rage, and the fact The X Games itself is a major aspect of the movie reflects this)