Updating this old thread, since the subject just came up. Valentine’s Day 2007 is still reported, so far as I see, as the last time Cornell had a “snow day”. Yet, as noted above, it was really only a half day. Classes weren’t canceled till 12:30pm.
https://web.archive.org/web/20070224005328/http://www.news.cornell.edu/stories/Feb07/snow.story.html
More recently, it looks like about once every two years or so they’ve called a late start day, where the very earliest classes were canceled and regular class schedules resumed at 10:10am, or 11:15am.
Since I’m sure you were all wondering, the first Cornell snow day ever was in March, 1971, allegedly.