It's quite obvious from the narrative that Theoclymenus is not describing an eclipse. He is viewing the suitors in the banquet hall and describes the vision he is having of their impending doom:
Shrouded in night are your heads and your faces and your knees beneath you; kindled is the sound of wailing, bathed in tears are your cheeks, and sprinkled with blood are the walls and the fair panels. And full of ghosts is the porch, full also the court, ghosts hastening down to Erebus beneath the darkness, and the sun has perished out of heaven and an evil mist covers all.
... the suitors laugh at him and tell him to go outside, if it is so dark in the hall. The vision of the "evil mist" is fulfilled poetically when Odysseus shoots Eurymachus "upon the breast beside the nipple" and his death agonies are described in the usual Homeric detail, ending with "and over his eyes the mist (achlys) poured down."
...and Zeus thundered loud, showing forth his signs. Then glad at heart was the much-enduring, noble Odysseus that the son of crooked-counseling Cronos sent him an omen,...
Unfortunately, I doubt this will be much help in dating the event :-)