date_ranges.py

from datetime import datetime, timedelta

def parse_date_ranges(dates):
    if(not dates or not len(dates) > 0):
        return False

    # make sure to order dates
    dates.sort()
    
    # init values
    result  = []
    tupl    = [dates[0], dates[0]]
    it      = iter(dates)
    date    = True

    def add_tuple_to_result(tuple):
        # if first part of tuple differs from last part -> add full tuple
        # else -> add first part of tuple only
        result.append(tupl if tupl[0] != tupl[1] else tupl[0])

    while date:
        # get next date or False if no next date
        date = next(it, False)

        # filter double dates
        if(date in tupl):
            continue

        elif(date):
            if(date - timedelta(days=1) == tupl[1]):
                # consecutive date, so add date to end of current tuple
                tupl[1] = date
            else:
                # gap larger than 1 day: add current tuple to result
                # and create new tuple
                add_tuple_to_result(tupl)
                tupl = [date, date]

        else:
            # date == false, so this is the last step.
            # add the current tuple to result
            add_tuple_to_result(tupl)

    return result
    
dates = [
  datetime(2014, 10, 11), 

  datetime(2014, 10, 1), 
  datetime(2014, 10, 2),
  datetime(2014, 10, 3),

  datetime(2014, 10, 5), 
  datetime(2014, 10, 5), 
  datetime(2014, 10, 6), 

  datetime(2014, 10, 22), 
  datetime(2014, 10, 20),
  datetime(2014, 10, 21),
  
  datetime(2014, 10, 9), 
   
  datetime(2014, 10, 7),
  datetime(2014, 10, 6)
]

expect = [
  [datetime(2014, 10, 1), datetime(2014, 10, 3)],
  [datetime(2014, 10, 5), datetime(2014, 10, 7)],
   datetime(2014, 10, 9),
   datetime(2014, 10, 11),
  [datetime(2014, 10, 20), datetime(2014, 10, 22)]
]

result = parse_date_ranges(dates)
print result == expect

dates.sort(reverse=True)
result = parse_date_ranges(dates)
print result == expect

dates = []
result = parse_date_ranges(dates)
print result == False

dates = [datetime(2014, 10, 6)]
result = parse_date_ranges(dates)
print result == [datetime(2014, 10, 6)]

dates = [datetime(2014, 10, 6), datetime(2014, 10, 5)]
result = parse_date_ranges(dates)
print result == [[datetime(2014, 10, 5), datetime(2014, 10, 6)]]

dates = [datetime(2014, 10, 6), datetime(2014, 10, 5), datetime(2014, 10, 7)]
result = parse_date_ranges(dates)
print result == [[datetime(2014, 10, 5), datetime(2014, 10, 7)]]