Why your devices show January 1, 1970 when timekeeping fails

Why 1970 keeps appearing on your devices

If you have ever spotted the date January 1, 1970 on a phone, laptop or app, the machine is not broken in a mysterious way. According to Engadget, that date is the starting point of Unix time, the system most non-Windows computers use to track the clock. When a device fails to read the time or receives a value of zero, it falls back to that starting point.

Unix was one of the first operating systems that would look modern today, and its development began in the late 1960s. Many later systems are described as Unix-like, including Linux, macOS and Android. Windows is the main exception, which is why the 1970 date rarely appears on Microsoft machines.

How Unix time works

Unix time counts the number of seconds that have passed since midnight UTC on January 1, 1970. UTC, or Coordinated Universal Time, is the standard reference for time across time zones, so it made a sensible anchor. The developers chose the date as an arbitrary but round starting point after earlier attempts based on the system clock speed ran out of room in less than 2.5 years.

Counting seconds makes life simple for a computer. Comparing two numbers is far easier than applying all the human rules around calendars and time zones. The system converts the raw count, plus your time zone's offset from UTC, into a readable date and time.

If you live in a time zone behind UTC, a failed time check can show late in the day on December 31, 1969 instead, because the zero value is shifted by your local offset.

The year 2038 problem

Traditional Unix time is stored as a signed 32-bit integer, a binary number with 32 digits. Because one bit records whether the value is positive or negative, the highest count it can hold is 2,147,483,647 seconds. That limit will be reached on January 19, 2038 at 3:14:07 AM UTC.

After that moment, the leftmost bit flips and the number is read as negative. The clock would then show December 13, 1901 at 8:45:52 PM UTC and count up from there. Engadget notes this is why the issue is known as the year 2038 problem.

There is plenty of time to prepare. Most modern Unix-like systems already use a 64-bit integer, which can count seconds for roughly 292 billion years before overflowing. A modern MacBook will cope fine, while a 32-bit device such as an iPhone 4 will not.

Who is affected in 2038

The main risk lies with older systems that are hard to update, such as the embedded computers inside appliances, vehicles and cameras. Some of these will not suffer much if they lose the exact time, but any device where accurate timekeeping matters will need replacing if it is still running in 2038.

People sometimes compare this with Y2K, the year 2000 problem. Both involve computers and time, but the causes differ. Y2K came from a decimal shortcut: programmers stored years as two digits to save expensive memory, so 2000 could be misread as 1900. The scare proved less severe than feared, though opinions differ on whether prevention work or an overstated risk deserves the credit.

Other ways computers keep time

Unix time is not the only approach. Many machines contain a real-time clock, which behaves like a wall clock and keeps running from a CMOS battery when the computer is off. If that battery dies, the clock will drift or reset.

Windows counts time differently, measuring 100-nanosecond ticks from midnight UTC on January 1, 1601. Engadget explains the date was not random: the Gregorian calendar repeats on a full cycle, and 1601 began the most recent cycle when Windows was being developed. As an unsigned 64-bit value, this method will not run out until September 14, 30,828.

Finally, the Network Time Protocol, or NTP, syncs computers to highly accurate time servers over the internet, correcting any drift. Leap seconds, daylight saving and time zone changes add further complications to a task that sounds simple.