preferred_time=2014-07-21 12:00:00
  current_time=2014-07-21 12:00:00
      ref_time=2014-07-24 00:00:00

#    X             preferred_time
#  |___________|   main
# |_______|        exclude
#            |___| nested


weekday=friday 00:00-24:00
timeperiod=nested

speday=wednesday 3 - wednesday 4 00:00-24:00
exclusion=nested
timeperiod=exclude

speday=2014-07-21 - 2014-07-27 00:00-24:00
exclusion=exclude
timeperiod=main
