Was confused about this myself, but I think I've worked it out :-D I found the documentation about the range lookup option very helpful.
When you do:
YourModel.objects.filter(datetime_published__year='2008',
datetime_published__month='03',
datetime_published__day='27')
The SQL will look something like:
SELECT ... WHERE EXTRACT('year' FROM pub_date) = '2008'
AND EXTRACT('month' FROM pub_date) = '03'
AND EXTRACT('day' FROM pub_date) = '27';
Whereas this part of django's generic date based views:
{'date_time_field__range': (datetime.datetime.combine(date, datetime.time.min),
datetime.datetime.combine(date, datetime.time.max))}
becomes something like:
YourModel.objects.filter(datetime_published__range=(
datetime.datetime.combine('2008-03-27',datetime.time.min),
datetime.datetime.combine('2008-03-27',datetime.time.max)
)
which produces SQL along the lines of:
SELECT ... WHERE datetime_published BETWEEN '2008-03-27 00:00:00'
AND '2008-03-27 23:59:59';
(the format of the timestamp in the last SQL example is wrong obviously, but you get the idea)
Hope that answers your question :)