datechunk.py

def datechunk(start, end, days):
    """
    Create a generator of (start_date, end_date) tuples 
    where the difference between start_date and end_date 
    is the number of days given.

    >>> list(datechunk(datetime.date(2010, 01, 01), datetime.date(2010, 08, 20), 30))
    [(datetime.date(2010, 1, 1), datetime.date(2010, 1, 31)),
     (datetime.date(2010, 2, 1), datetime.date(2010, 3, 3)),
     (datetime.date(2010, 3, 4), datetime.date(2010, 4, 3)),
     (datetime.date(2010, 4, 4), datetime.date(2010, 5, 4)),
     (datetime.date(2010, 5, 5), datetime.date(2010, 6, 4)),
     (datetime.date(2010, 6, 5), datetime.date(2010, 7, 5)),
     (datetime.date(2010, 7, 6), datetime.date(2010, 8, 5)),
     (datetime.date(2010, 8, 6), datetime.date(2010, 8, 20))]

    """
    import datetime

    curr = start
    while True:
        if curr+datetime.timedelta(days) > end:
            yield (curr, end)
            break
        yield (curr, curr+datetime.timedelta(days))
        curr = curr + datetime.timedelta(days+1)