The expressions in these verses are all wishes that the day of Job's birth would no longer exist. This may imply that the day, although in the past, still existed somehow. The UDB translates them as expressions of sadness about what that day was like.
These two clauses describe the darkness of the day of Job's birth, thus repeating Job's regret that he had been born. (See: [[rc://en/ta/man/translate/figs-parallelism]])