Hi Ann,
There are exceptions to the rule and these are quite frequent when using 'an' .
I would say 'année' is used more frequently than 'an'.
We say -
L' an 0
Le nouvel an
L'an 2000
'Le Nouvel an chinois 2019 est l'année du cochon'
is an example when talking about the same year using both words.
Not easy ....