The seasonal stream is starting at 1692482400!

100 million seconds (about 3 years, 2 months, and 1 day) seems to be about the length of a cultural era on the Internet.

Or in simpler units we could call it 52 A.D.U

I think one of the coolest things with unix timestamp filenames is that you're preserving some knowledge just with the filename. Like this Sanae image here. I can't remember when touhou flipside's "fat Sanae" thing took off personally, but I know it was a little bit before I saved this image so I can say it's sometime in early-mid 2017.
I don't think history as a whole will need this specific information, but at some point people in the future people might care about dating specific events and could use such filenames. You can piece together a timeline of events.
I'm kind of surprised news organizations don't try to track stuff down with it, but I guess ignorance of such things is to be expected.