The Mists of Ravenloft can travel through time as well as space...thus they could go back in time (or maybe even
forward through time) to bring someone to Ravenloft's present day.
So you technically could have someone from Faerun 100 years ago plucked up by the Mists and someone from present day Faerun plucked up and they might be deposited in Ravenloft from 15 years ago.
Likewise, those who manage to escape can sometimes arrive minutes after they left, even though years may have passed in Ravenloft...or they may even return
before they left! We'd prefer, though, to have outlander characters be from the "present day" of the world they've left behind...it makes things easier to manage.
Generally speaking, the timeline is about the same as other worlds...I have a timeline by John W. Mangrum that I should dig out that had comparitive years of Ravenloft vs. Forgotten Realms, Greyhawk, and Dragonlance. However, with the Mists' ability to travel through time, the time in Ravenloft relative to other worlds is irrelevant.