In general https://www.web-rewind.com/xywz takes you to year xywz (if exists) but 1999 for some reason takes you to an overview of all years.

edit: https://www.web-rewind.com/1999 would take you to an overview of all years but now it takes you to year 1999

I think that overview appears on every year after x visited artifacts. For me, it appeared in 2002.