according to Numista's catalog guidelines
-- Specify the year of minting in the selected calendar, if it is shown on the coin. Note that the year of minting may be different from the year the coin was released into circulation.
so there are 3 "year"s:
the year of minting
the year of coin put into circulation/market
the year on the coin
I have two questions
1) if "the year of minting" is what it literally means, then for a coin released into circulating on January 15th 1999, it is hard to tell it is minted in December 1998 or January 1999. Also "the year of minting" is not important in this context.
2) what should the year line be for these 2 coins:
this coin is released into circulation in 2006, but the date on the coin is 2008
this coin is released into circulation in 2021, but the date on the coin is 2022
or "the year shown on the coin" is a better name for "the year of minting", then the two questions get solved.