Twitter doesn't want you to miss anything important, and that's why it's introducing "while you were away" headings on tweets.
It's available on iOS already, and for Android and twitter.com to follow, soon. No date specified.
Recaps, marked with a “While you were away” heading, will begin to appear for all Twitter for iOS users today, and on our Android app and twitter.com soon.Twitter's Introduces "While you were away" [blog.twitter.com]
This sounds similar to one of the other experiments it was running.
New Twitter Experiments With Your Home Timeline [webmasterworld.com]
