Why February 29 is the day to go wild on social media

Remember the days when social media wasn't everywhere? Where you could go to a party and try out your most embarrassing dance moves, without thinking about how this would crop up in "on this day" reminders every year?

Saturday could be the day where that dream becomes a reality. It's February 29, the extra day added to a year every four years. While it's become the butt of many jokes, with those unlucky to be born on the day having to wait four times longer to reach adulthood, it could provide a rare opportunity to forget your regret.

A Twitter user called "ashersmi" made the observation Wednesday: "it’s a leap year so whatever you do on saturday won’t show up on snapchat memories for another 4 years so basically no rules no regrets." That also means no TimeHop, Facebook Memories, Apple and Google retrospectives.

Or does it?

The tweet cuts to a big issue in computer programming, where an otherwise-predictable series of dates gets interrupted every four years by a rogue day. This is because while a day marks one rotation of the Earth, a year is supposed to mark one orbit of the Earth around the Sun. Problem is, the Earth actually takes 365.24219 days to orbit. The Gregorian calendar, introduced in 1582, sought to solve this growing discrepancy.

Leap years have been around for nearly 500 years, but computers in the past century have still struggled. In 2016 an airport in Germany started refusing luggage as the system wouldn't recognize the tags. Microsoft Zunes everywhere started failing in 2008 due to the way the MP3 player handled leap years. A computer glitch in 1997 in New Zealand ended up costing NZ$1 million ($630,000).

So what does that mean for these retrospective features, designed to dredge up the best and worst on the photo's anniversary?

In the case of Facebook, it will indeed remain hidden. A company spokesperson confirmed to Inverse that memories from February 29 are confined to that day, which means they only surface every four years.

The same is true for TimeHop. Matt Raoul, CEO of TimeHop, tells Inverse that the app "works time-machine style, and is specific to that actual calendar date."

"So on Feb 29th, folks will see memories they haven’t seen in four years," Raoul says. "Any memories you create on Feb 29, 2020 will go into some vortex for until they pop up again in 2024. Should be a pretty fun day."

Inverse also contacted Snapchat, Apple and Google for comment but none were able to shed light ahead of publication.

A previous glitch with Facebook may reveal a bit about how the system works. A bug encountered on December 31, 2015, started telling people that on this day they'd become friends with a random user 46 years ago. This was despite the fact Facebook launched in 2004.

While 46 years ago probably wasn't the start of a Facebook friendship, it was the start of Unix time. This is the number of seconds that have passed since January 1, 1970, and it's used by a number of modern systems to store dates. The glitch suggested that Facebook's "on this day" feature, at some stage, depends on Unix time.

While that could explain how these systems can handle strange days like February 29, Unix time comes with its own set of potential issues. The Y2038 bug is predicted to hit older machines in around 18 years time, when the number of seconds becomes too long for some systems to handle. Leap seconds, used to keep the days synced up with the Earth's rotation, have also caused havoc for airlines running on Unix time.

At least in the case of TimeHop, it seems February 29's memories will indeed fade into obscurity. That doesn't mean people have stopped asking, wondering if they're in the clear for the next four years.