O japanese calendar, in its original form, does not count years like our Gregorian calendar.
The traditional Japanese calendar is based on eras, where counting is restarted whenever one era ends and another starts.
These days, the most used calendar in Japan is the Gregorian calendar, which counts the days, months and years in the same way we do in Brazil and many western countries.
Despite this, many public registries and registries still use the traditional calendar, forcing people to know and use both the traditional Japanese calendar and the Gregorian calendar.
The traditional Japanese calendar
Contrary to what we are used to, the traditional Japanese calendar does not count the years like ours.
It counts years based on time periods marked by major events.
In the past, this event could have been anything landmark, like the birth of someone important to Japan, a revolution in the economy, the death of someone famous.
The fact is, when an era begins, the counting of years begins again and goes on counting the years until a new era appears.
Over time, these “eras” of the Japanese calendar came to mark only the beginning and end of the reign of each Japanese emperor.
So when an emperor takes the throne a new age begins, and when he dies the current age ends.
According to this form of calendar, the year 2010 corresponds to the 21st year of the era. 平成, since it has been 21 years since Emperor Akihito assumed the Japanese throne.
In case you're curious, below is a list of the more recent eras:
| eras | name of eras | Time course | Emperor |
|---|---|---|---|
| 明治 | Was Meiji | 1868 to 1912 | Emperor Mutsuhito |
| 大正 | Was Taishou | 1912 to 1926 | Emperor Yoshihito |
| 昭和 | Was shouwa | 1926 to 1989 | Emperor Hirohito |
| 平成 | Was heisei | 1989 to 2019 | Emperor Akihito |
| 令和 | Was Reiwa | 2019 - present | Emperor Reiwa |
We say that whoever is born within an era of the Japanese calendar is born in the year of that era. For example, I was born in the year 55 of the Shouwa era, ie 1981.
And the Western calendar?
Because of Western influence, the Japanese began to use the Gregorian counting system along with many of the Japanese symbols used to represent the days of the week in japanese, the months of the year in japanese it's the year in japanese itself.
Interestingly enough, numbers on Japanese calendars are often written with Indo-Arabic symbols (the same numbers we use) instead of numbers in japanese.
Because of this mix of japanese symbols, Indo-Arabic numbers and japanese accountants, a mixture of the Japanese calendar with the Gregorian calendar was created.
In the end, this japanese-gregorian calendar it was the calendar adopted by the Japanese in their day-to-day, however public bodies and official documents only accept dates written according to the traditional calendar, forcing the coexistence between the two counting systems.