I had a feeling like this the first time I did shrooms. Perhaps because it was the first time I experienced that time is relative (I always knew it because of reading alot of Einsteins Relativity theory, but I never felt it myself).
I tried to look at the clock for one minute, I had the feeling it took like half an hour. It seemed like a 1000 things happend in that minute. And to be honest, I never saw the clock switch to next minute =p... It just took too long!