How to fetch old data from twitter - python-2.7

Question

I am using tweepy api to fetch old tweets
Here is my code which only fetching around most recent 3200 tweets from twitter.
Code :
import tweepy #https://github.com/tweepy/tweepy
import pymssql
#Twitter API credentials
access_key = ''
access_secret = ''
consumer_key = ''
consumer_secret = ''
#connect to local database
conn = pymssql.connect('(local)','','','mydbname')
x = conn.cursor()
def get_all_tweets(sc):
#authorize twitter, initialize tweepy
auth = tweepy.OAuthHandler(consumer_key, consumer_secret)
auth.set_access_token(access_key, access_secret)
api = tweepy.API(auth)
#initialize a list to hold all the tweepy Tweets
alltweets = []
#make initial request for most recent tweets (200 is the maximum allowed count)
new_tweets = api.user_timeline(screen_name = sc,count=200)
#save most recent tweets
alltweets.extend(new_tweets)
#save the id of the oldest tweet less one
oldest = alltweets[-1].id - 1
#keep grabbing tweets until there are no tweets left to grab
while len(new_tweets) > 0:
print "getting tweets before %s" % (oldest)
#all subsiquent requests use the max_id param to prevent duplicates
new_tweets = api.user_timeline(screen_name = sc,count=200,max_id=oldest)
#save most recent tweets
alltweets.extend(new_tweets)
#update the id of the oldest tweet less one
oldest = alltweets[-1].id - 1
print "...%s tweets downloaded so far" % (len(alltweets))
print len(alltweets)
#save tweets to database
for tweet in alltweets:
insert_post_details(tweet)
#insert tweets data into database
def insert_post_details(tweet):
try:
qry="INSERT INTO MPTTwitterPosts(Id,Created_At,Favorite_Count ,Retweet_Count,Text) VALUES(%s,%s,%s,%s,%s)"
x.execute(qry, (str(tweet.id), tweet.created_at,tweet.favorite_count,tweet.retweet_count,str(tweet.text.encode("utf-8","ignore"))))
conn.commit()
except Exception,e:
print str(e)
if __name__ == '__main__':
#pass in the username of the account you want to download
get_all_tweets("Google")
If I tried to get older tweets with max_id,it is giving blank list of tweets
so How can I get old tweets, any suggestion would be greatly helpfull.
Thanks