Not too strange though, several countries do this, although usually mixed with the Gregorian calendar. Japan uses both the Gregorian calendar and its own calend

Not too strange though, several countries do this, although usually mixed with the Gregorian calendar. Japan uses both the Gregorian calendar and its own calendar where years are counted from the start of the reign of the reigning emperor. This year 2016 is Heisei 28; the year 1980 was Shōwa 55. This system is often used on formal documents and one's date of birth.