I wouldn't say the Japanese calendar is used for "most" activity. As far as I can tell, the Japanese calendar is certainly used for things like government form

I wouldn't say the Japanese calendar is used for "most" activity. As far as I can tell, the Japanese calendar is certainly used for things like government forms, but for non-government stuff, not so much. If I buy tickets for something online, for instance, the web form asks for my birthdate using the normal Gregorian calendar year. Even the government stuff is a mix; my residence card shows my birthdate and card expiration date with the Gregorian year.