What is the irony in the words "festival" and "carnival" in the poem "This is the dark time my love" by Martin Carter?

Theis in the juxtaposition of
normally pleasant words with words that are very unpleasant.

Irony is when something is unexpected.  You would expect a festival to be fun and
games, and you would expect a carnival to be similarly harmless.  In this case, though, the
words are used to describe a lot of somethingbad things.

It is the season of oppression, dark metal, and tears.
It is the festival of
guns, the carnival of misery

The word festival is contradicted by guns and the word
carnival is contradicted by misery.

The dark time is not a time of
peace.  It is a time when you are a target.  While you are sleeping, the enemy is coming for
you.