Internet Explorer 11 - Cookies not saving passed session.

I'm having an issue with Internet Explorer 11, the issue we have is that our cookies dosen't save passed session, so as soon as a customer kills the browser and then starts it up again the cookies are gone in the wind.

info:

1. Website is a Python based website.
2. Cookies get set using Simple Cookie from python.
3. Cookies have an expire reaching for 1 year.
4. Cookies have the correct path.(Path is set to '/')
5. Cookies have the correct domain.
6. We are able to extract data from the cookie during session. 

What i've checked/done:

1. Checked Safety Mode to make sure it's not on and not preventing the cookies to be set.
2. Double checked the cookies to make sure they are actually getting set and they are, they are there.
3. Made sure the cookies get set correctly and are readable by internet explorer.
4. Checked other browsers(Chrome, Firefox) They work perfectly fine there, the  issue seams limited to IE11.

Code where cookies are saved looks like this(Python):

**self.cookie is Simple Cookie.

**data is a string

expiration = datetime.datetime.now() + datetime.timedelta(seconds=3600*24*365)
self.cookie[self.prepend + key] = data
self.cookie[self.prepend + key]['expires'] = expiration.strftime('%a, %d-%b-%Y %H:%M:%S PST')
self.cookie[self.prepend + key]['domain'] = self.domainself.cookie[self.prepend + key]['path'] = '/'

If you need any more information from me, just ask and i provide it if possible, i would be grateful for your help as i can't figure this one out.