Email wasn’t hugely popular until the 1990s, but confused iPhone users have recently reported receiving ghost emails that contain no subject and no message supposedly sent from January 1970.

Fortunately, according to the U.K.’s Mirror, the confusing emails stem from a glitch in the operating software of iPhones and iPads, instead of being something more malicious, such as a virus. The glitch is thought to occur when a user checks their email in a different timezone from their usual one.

Jan. 1, 1970, the timestamp of the confusing emails, represents zero in UNIX time, which is code computers use to understand and compute time. So when an email is sent without any data, or with the timezone bug, the Apple operating software defaults the date to zero — hence Jan. 1, 1970.

To fix the bug, the user has to perform a “hard reset,” which is done by holding the device’s “lock” and “home” button until the device restarts.

Of course, people were not able to send email in 1970 because it was not yet invented. The first electronic mail message wasn’t sent until 1971 by Ray Tomlinson, who died last Saturday at the age of 74.

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