every year vs each year

every year and each year both are adverbs.

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

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

Other synonyms of every year include annually, yearly.

every year (adverb)	each 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)