first year of an era; inaugural year of a reign era
Used in Japanese era dating for the first year of an imperial era name; e.g. 令和元年 means the first year of Reiwa, not 令和一年 in formal date style.
We got married in the first year of Reiwa.
The first year of Heisei is 1989.
first year of a new development; year when something began
Figurative use for the year an important trend, industry, technology, or movement is considered to have started; common in media-style phrases like AI元年.
2024 is sometimes called the first year of generative AI.
That tournament became the starting year for the popularity of women's soccer.
A new era began in the first year of Reiwa.
2020 is said to be the year remote work truly began.