Refers to a historical era or the starting point of a calendar system, such as 紀元前 (BC) or 紀元後 (AD). Often used in historical contexts.
These ruins date from the 3rd century BC.
キリスト紀元は西洋の暦の基準である。
The Christian era is the basis of the Western calendar.
Common Era; AD
Specifically denotes the Common Era (CE) or Anno Domini (AD). Used in expressions like 紀元前 (BC) and 紀元後 (AD).
紀元前200年と紀元後200年では400年の差がある。
There is a 400-year difference between 200 BC and AD 200.
Around 3000 BC, civilization began in Egypt.
This discovery came to mark a new epoch in the history of science.
The spread of the internet ushered in a new era.
new era; new age
Buddhist calendar; Buddhist era