Sometimes I read a line like this:
"... for many a year." "...many a time..."
Is it talking about many years?

Why we add 'a' into these sentences?
Its a hangover from English of the past. It is now only rarely used.

However, like all such things of this nature, its use survives in literature, in songs and in poetry, and it is not uncommon to find phrases like this even in modern songs.

Many's the time I have seen this. Emotion: smile