Abdication of Emperor Akihito could trigger Japan’s Y2K millennium bug

On 30 April 2019, Emperor Akihito of Japan is expected to abdicate the chrysanthemum throne. The decision was announced in December 2017 so as to ensure an orderly transition to Akihito’s son, Naruhito, but the coronation could cause concerns in an unlikely place: the technology sector.

The Japanese calendar counts up from the coronation of a new emperor, using not the name of the emperor, but the name of the era they herald. Akihito’s coronation in January 1989 marked the beginning of the Heisei era, and the end of the Shōwa era that preceded him; and Naruhito’s coronation will itself mark another new era.

But that brings problems. For one, Akihito has been on the throne for almost the entirety of the information age, meaning that many systems have never had to deal with a switchover in era. For another, the official name of Naruhito’s era has yet to be announced, causing concern for diary publishers, calendar printers and international standards bodies.

It’s why some are calling it “Japan’s Y2K problem”.

“The magnitude of this event on computing systems using the Japanese Calendar may be similar to the Y2K event with the Gregorian Calendar,” said Microsoft’s Shawn Steele. “For the Y2K event, there was world-wide recognition of the upcoming change, resulting in governments and software vendors beginning to work on solutions for that problem several years before 1 Jan 2000. Even with that preparation many organisations encountered problems due to the millennial transition.

“Fortunately, this is a rare event, however it means that most software has not been tested to ensure that it will behave with an additional era.”

Microsoft issued a software update in April that let developers test what would happen to their software after the era switches over. Steele warned coders of what to look out for: “Some algorithms attempting to count the years during a transition year may not consider the possibility of two partial Japanese Calendar years, in two different Calendars Eras, within the same Gregorian year,” for instance. Other applications may crash if they try and parse a date which will never exist – for instance, 40 of the Heisei era, which will actually be year 10 of the next era.

A much harder problem faces Unicode, the international standards organisation which most famously controls the introduction of new emojis to the world. Since Japanese computers use one character to represent the entire era name (compressing Heisei into ㍻ rather than 平成, for instance), Unicode needs to set the standard for that new character. But it can’t do that until it knows what it’s called, and it won’t know that until late February at best. Unfortunately, version 12 of Unicode is due to come out in early March, which means it needs to be finished before then, and can’t be delayed.

“The UTC cannot afford to make any mistakes here, nor can it just *guess* and release the code point early,” Unicode’s Ken Whistler wrote in a message to the organisation earlier this month. “All of this is pointing directly to the necessity of issuing a Unicode 12.1 release sharply on the heels of Unicode 12.0, incorporating the addition of the new Japanese era name character, which all vendors will be under great pressure to immediately support in 2019 software releases.”

The era system doesn’t only pose problems during an imperial transition. Many older computers, with aspects dating back to before the end of the Shōwa era in 1989, have never been updated to reflect the new era, and still think the year is Shōwa 93. That means Japan could face another mini Y2K problem in 2025, as those systems attempt to tick over to a three digit Shōwa year they can’t cope with.

Some Japanese bodies are attacking the problem from the other end. In May, the country’s national tax agency announced it was considering continuing Heisei dates after the switchover, in an effort to avoid confusion in tax payments.