noun
East Asian age reckoning; traditional age counting
Refers to the traditional system where a person is considered one year old at birth and gains a year on New Year's Day, rather than on their birthday.
日本では、昔は数え年で年齢を数えていました。
In Japan, people used to count their age by the traditional East Asian age reckoning system.
数え年
Under the traditional age reckoning, you are one year old at birth, and everyone gains a year when New Year's Day arrives.