Was or is or both? A line from the Prologue to The Canterbury Tales

Perhaps this sentence could be viewed as a linking of two thoughts:

He was fresh.

The month of May is fresh.

The was in the first thought describes the state of the subject in the literary passage.

The is in the linked thought is describing the freshness of May (flowers and trees budding; seasons changing to Spring). The present tense is used because May's freshness is eternal.

I'm thinking that it's a simple sentence, with a complement clause of fresh is the month of May.

Since the sentence uses like or as, I would classify this is a simile. And this other answer may confirm.