Japan could be facing its own version of the Y2K bug, with Unicode also affected. It’s all to do with the upcoming abdication of Emperor Akihito.
As The Guardian notes, Japan’s date system resets every time a new emperor take over, marking what’s considered a new historical order. Emperor Akihito announced last December that he’ll be stepping down at the end of April 2019, ending the Heisei era that’s currently in year 30.
The problem is that many computer systems and applications which use the Japanese year system have been designed since the Heisei era began in 1989 and thus there’s never been much reason to think about how computers would handle either the resetting of the date or the way some periods being measures or analysed would straddle two eras. (By way of context, the previous era began in 1929.)
Microsoft has addressed the issue by including a placeholder in Windows 10 in the form of a registry key that simulates a new, unnamed era beginning. The idea is to allow software testing to see if any problems arise; if they do, the registry entry can simply be removed to get everything back to normal working order before starting to develop a fix.
Another problem is that despite the advance warning of the transition, the new era won’t be named until a matter of weeks before the transition. That’s a challenge for calendar and diary makers, but also unfortunate timing for the Unicode system.
While the name of the Heisei era is made up of two characters in Japanese writing, Unicode represents it in a single combined character. That approach will likely be used for the new era’s name, but it will be revealed too late for the upcoming Unicode 12 release. That means not only that not only will a version 12.1 have to be released just a matter of weeks later, but it will need to be supported immediately in any software that could have to handle Japanese dates.