The 年号 system

Japan uses the Gregorian calendar (because everone else does), and is familiar with Western year numbering. However, it still uses the "nengou" (年号) regnal year system in some situations.

For example, Japanese hospitals issue ID cards for patients, and those ID cards list the patient's birthdate. However, instead of my birth year, it says 昭和50 (Showa 50), referring to the 50th year of Emperor Hirohito's reign. Culturally, it can also refer to a certain generation. At this point, even the youngest person born in the Showa era (before 1989) is over 30 years old.

This is an online ad that I saw. It starts with 「白髪多い昭和生まれは」, meaning "people born in Showa with a lot of white hair..."

I thought that was interesting.