each year vs every year

each year and every year both are adverbs.

Word	Noun	Adjective	Verb	Adverb
each year	No	No	No	Yes
every year	No	No	No	Yes

As adverbs, each year and every year are synonyms defined as:

Other synonyms of each year include annually, yearly.

each year (adverb)	every year (adverb)
without missing a year	without missing a year
by the year; every year (usually with reference to a sum of money paid or received)