A company spokesperson told Bloomberg that the team is currently fixing the bug "so everyone can ring in 2016 feeling young again" but didn't expound on what it is. According to some computer experts such as Microsoft Developer Mark Davis, though, the culprit is most likely the Unix operating system used by most data centers.
Unix's internal calendar has an arbitrarily assigned starting point called "epoch" with an internal value of "0." The OS calculates for time by counting seconds from that day. Guess what date this starting point is -- that's right, it's January 1st, 1970, which is 46 years ago today.
Davis wrote on Facebook:
...if you click on your "Memories page, you'll see a subset of your friends listed as having a 46-year-old Facebook memory today. Scrolling through my list, it's indeed people I've been friends with on Facebook for a very long time -- chances are, the "Friends with since" feature was implemented AFTER I became friends with those people. And as such, it's stored in the database as "0" rather than the actual date.
He added that the developers who wrote the feature should have included a line in their codes that instruct it not to use the "0" value as the "Friends with since" starting date. This Unix glitch, by the way, is quite common, and it's not unusual for gadgets' clocks and calendars to switch to December 31st, 1969. We doubt you'd want to spend the first day of 2016 talking about Unix, but hey, at least you don't have to do your research in the middle of your family's New Year party when your grandparents ask.