You could have a look to the _utc_transition_times memberof the timezone you're using.
>>> from pytz import timezone
>>> tz = timezone("Europe/Paris")
>>> print tz._utc_transition_times
[datetime.datetime(1, 1, 1, 0, 0), datetime.datetime(1911, 3, 10, 23, 51, 39), datetime.datetime(1916, 6, 14, 23, 0), datetime.datetime(1916, 10, 1, 23, 0), date
....
datetime.datetime(2037, 3, 29, 1, 0), datetime.datetime(2037, 10, 25, 1, 0)]
It will give you the list of the DST change dates (start and end of DST).
According to the code of tzinfo.py
class DstTzInfo(BaseTzInfo):
'''A timezone that has a variable offset from UTC
The offset might change if daylight savings time comes into effect,
or at a point in history when the region decides to change their
timezone definition.
'''
# Overridden in subclass
_utc_transition_times = None # Sorted list of DST transition times in UTC
_transition_info = None # [(utcoffset, dstoffset, tzname)] corresponding
# to _utc_transition_times entries
So if you mix the _utc_transition_times with _transition_info you will grab all your needed informations, date, time and offset to apply ;)
