Do People in Comas Sense Passage of Time?

I have always been fascinated with the story of Rip Van Winkel. Do people who stay in comas for long periods have any perception of time?
If you went under in 1970, say, and woke up today, would you have any idea that 40 years had gone by?
Of course, people would wonder if you asked about disco music and where to buy a leisure suit!

According to Wiki, Terry Wallis was not aware that almost 20 years had passed while he was in a minimally conscious state.

On the other hand, Jan Grzebski claimed to have been aware of his family speaking to him during his twenty year coma, but was unable to respond to them in any way.