As adverbs the difference between yester and yestern
is that
yester is (archaic) yesterday while
yestern is yesterday.
As adjectives the difference between yester and yestern
is that
yester is (archaic) last; last past; next before; of or pertaining to yesterday while
yestern is (archaic|rare) of or pertaining to yesterday.
As nouns the difference between yester and yestern
is that
yester is (archaic) yesterday while
yestern is yesterday.