Facebook is testing a News Feed filter across its Web and mobile apps called ‘On This Day’ which – as is probably pretty self-explanatory – shows a list of content and status updates published on the social network exactly a year ago.

For a number of users with the most recent Facebook design on the Web, the option is available by hitting the downward arrow underneath the News Feed categories in the top right-hand corner of the page.

Facebook then displays a header image taken from a photo or gallery uploaded that day – in this case July 31, 2012 – with the tagline ‘What your friends were up to a year ago today.’ A list of notable content is then assembled underneath, giving users the ability to take a quick trip down memory lane.

fb11 Facebook testing On This Day tab in the News Feed to help users take a trip down memory lane

The various posts and status updates aren’t assembled in chronological order, suggesting that Facebook is testing a rather more complex algorithm to keep users engaged with the feature.

Inside Facebook notes that for some users, there’s also a sidebar showing other notable events that occurred around this time. These are split into ‘Your Friends On This Day’ and ‘Your Friends This Month’, which show other interesting nuggets of information from years gone by. The News Feed filter shows as the URL ‘facebook.com/feed/todayinhistory’, suggesting that a slight rebranding could also be on the cards before the feature is rolled out to all Facebook users.

From the Facebook iOS app, ‘On This Day’ is available to a select group of users by scrolling to the top of the News Feed and finding the necessary option in the expandable menu. It’s almost identical to the Web incarnation – minus the sidebar – but does seem to serve up posts and other content in a different order.

The feature isn’t a particularly new idea – Facebook introduced a similar feature also called ‘On This Day’ in August 2011. Given that the social network has been around for some time now, it’s a good opportunity for Facebook to leverage all of that ageing content in new and interesting ways.