A.  REM sleep  periods,  and therefore dreams,  last  typically in the
range of 5 to 45 minutes (cf.  section 6).  Often, the subjective time
spent  in a dream is much  longer.   One possible explanation for this
time-stretch effect  is  that  dreams are  combined  from  pieces (see
preceding   paragraph)  that   have their   own   different setting in
time.  You first dream of  something that occurred  a year ago, then -
following - of  something that occurred  just recently, mix them up  a
bit and are left with the remembrance of a dream that lasted a year.

But experiments suggest that dreamed actions run in "real time" - what
you do in your dream  takes exactly this time  to dream. With external
influences like the radio  running in the  morning, you have  both the
real time in which  you hear something  and - sometimes -  the feeling
that  it   lasted considerably longer.  Anyway,  time  is  one  of the
perceptions that are heavily distorted in dreams.