Does anyone know of any specific cases in which someone's perception of time has been drastically altered?

Usually any kind of human vice drugs, alcohol.





Working (as in can't get anything done).





Daydreaming can cause loss of perception of time; as well as certain confinements.





Sometimes just as simple as not having a watch or a brain on.





Expanded: There was an actual underground experiment with no reference to time (for several days).