If you’ve noticed your iPhone receiving emails from 1970—long before emails became popular—don’t be alarmed.

Some iPhone owners have been complaining on social sites and forums, including Twitter TWTR and Reddit, about receiving blank emails in their inboxes with a timestamp of “January 1, 1970,” as reported by The Telegraph on Monday. Images posted to Twitter show these emails do not identify a sender, and the messages have no content. They do, however, show the odd date.

Although it may be confusing and concerning, the issue appears to be little more than a bug affecting iOS-based devices that causes no lasting, harmful effect. According to posters on forum site Reddit, the issue stems back to Unix, a family of operating systems Apple AAPL has long relied upon for its own operating systems and the way it interprets time.

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In order to interpret time, Unix assumes that January 1, 1970 is zero, or the beginning of time, and each second thereafter is a point in time. As of this writing, there have been over 1.45 billion Unix instances of time. Those instances are then translated to a human’s understanding of time, and a real world date and time are delivered.

Unix time has become a bit of a cult phenomenon among the platform’s enthusiasts. When Unix time hits certain milestones—like when it did in 2009 with marker 1,234,567,890—Unix enthusiasts held special parties, according to a report in Wired. It’s not even uncommon for some enthusiasts to use Unix time when communicating dates.

So, what does this all have to do with the iPhone and emails? According to The Telegraph, the bug only seems to affect users who change timezones and check their email on an iOS-based device. The software, it seems, gets confused by the actual time and defaults to Unix zero, or January 1, 1970. According to several Reddit users, the issue can be fixed by soft-resetting the iOS-based device by holding down the power and home buttons simultaneously. Once the device is booted back up, the emails disappear.

Read more: The Founder of Email, Ray Tomlinson, Dies

Still, the issue is similar to another that cropped up last month when users were changing their iOS default dates to Unix zero, quickly discovering that doing so rendered their devices unusable. After users complained about the issue, Apple said last month it would fix the issue in a future software update.

Apple did not immediately respond to a request for comment on whether it will fix the latest 1970 glitch. It’s also unknown whether it impacts all iOS and OS X devices and which versions of its software are affected. That said, at this point, it appears to be somewhat limited and easily fixable.

And at least now you know what the beginning of time is—in Unix.