Occasionally Friendica has old posts in the timeline, e.g. when it refreshes pinned posts from a profile. But ever since yesterday there've been a lot more like:

5 years ago (Received 6 minutes ago)
...
15 years ago (Received 35 minutes ago)
...

From many different accounts. Seems like all of a sudden several people have gotten nostalgic and are resharing their old posts. Don't know what it is, maybe something in the weather, maybe escapism from today's world...