Some people have asked whether Windows supports new Japanese Calendar Emperor eras if that becomes necessary.  FWIW That information is stored in the registry on Win7/Win8/.Net4.0+:

 

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nls\Calendars\Japanese\Eras

There are string values for each of the supported eras.  Each value is named with the start date of the era in yyyy MM dd format, such as "1989 01 08" for the Era starting on January 8, 1989.  The data for each value is a string, with the Japanese Era name, both full, and abbreviated, and then English full and abbreviated names.  Those are delimited by underscores.  For example: "平成_平_Heisei_H".

Though you may not need a new era yet, it's possible to add a key if you want to, for example, to test and make sure your software won't break if another era gets added.

I blogged about that in more detail earlier at: http://blogs.msdn.com/b/shawnste/archive/2009/09/24/japanese-calendars-how-do-i-test-support-for-additional-eras.aspx