Used in IRC or other chat (in the negative) as a sarcastic comment to something already said or "old news."
<person_1> X just happened, check out website
<other people> Very interesting, person_1!
... 3 hours later ...
<person_2> OH EM GEE X JUST HAPPENED website
<other people/person_1> That's so not 0day.
<other people> Very interesting, person_1!
... 3 hours later ...
<person_2> OH EM GEE X JUST HAPPENED website
<other people/person_1> That's so not 0day.
by rmb September 04, 2006