Microsoft has pulled its first updates of the year for Office 2010 after reports, mostly from Japan, that they have been breaking Excel. 

The updates arrived on January 2 with changes in the Japanese calendar, most likely to reflect the changes coming with the end of Japanese Emperor Tenno Akihito's reign. He is planning to abdicate on April 30, 2019, marking the end of the Heisei era and ushering in an as yet unnamed new calendar era. 

As reported by Borncity, Microsoft pulled the January 2019 Office 2010 updates on January 5. All updates for Excel 2010 and Office 2010 included "changes to Japanese calendar". 

Japanese language blogs have reported that after installing the non-security updates, users were seeing messages that 'Excel cannot be opened' and that the spreadsheet app was sometimes freezing. Excel also couldn't handle new entries in cells. Users reported that uninstalling the updates resolved the issue.  

Microsoft's support note for the Excel 2010 update confirms it has been removed due to problems the update causes in Excel. 

"After you install this update, you may experience difficulties in Microsoft Excel or other applications. To resolve this, uninstall the update by following the instructions in the 'More information' section," Microsoft says. 

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Microsoft has previously written about the inter-era calendar bugs that could surface during and after the change in Japanese emperors. 

The company described it as "The Japanese Calendar's Y2K Moment", referring to the chaos expected as computers, which only used the last two digits to indicate a year, failed to distinguish between the years 2000 and 1900.  

"The magnitude of this event on computing systems using the Japanese Calendar may be similar to the Y2K event with the Gregorian Calendar," wrote 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 January 1, 2000.  Even with that preparation many organizations encountered problems due to the millennial transition."

Steele noted that after the era has changed it will be too late to test for compatibility problems. Microsoft included a special registry in the Windows 10 version 1803 to help developers spot problems before the change. 

There are all sorts of cross-era data problems that could occur during and after the transition. At transition, software with calendar controls that presume only one current era could stumble. Also, how will algorithms handle the same date expressed differently in two eras?

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