So you're saying you palpably felt when you woke up like you had just lived for days? You had experienced every minute of those days? Like Picard in the flute episode...what was it called again?
"The Inner Light"
Or are you saying days passed by? Because days can pass, but the moments within the dream in which you're "doing something" most likely did not add up to days. In that case, it would be "doing something for two minutes, then it's the afternoon, and you do something for five minutes, then it's the next morning and you do something for three minutes, and it's a day later." That's not actually having days experienced in your dream, just days pass by.
Probably more the latter than the former, I figured much more time had passed because it's the only way for so much to have occured. I "filled in the gaps" as it were. You could also reason that since many people don't even remember their dreams anyway that that time happened we just didn't remember them so from our own POV they never occured.
But, yes, there's been times when I've had a dream where a lot of time seemed to have passed and a look at the clock upon waking up and was surprised to see how much little time had passed since the last time I looked at the clock (before falling asleep/between sleep cycles.)