The US Balao-class and Gato-class submarines had enough provisions to stay on patrol for 75 days under normal operating conditions. Information on other long-range submarines has proved hard to find, although this site mentions that British O, P and R class submarines had a range of 20,000 miles, but there is no mention of actual or possible duration at sea without being resupplied. What I am looking for here is the longest period submariners went without being able to set foot on (friendly) land.
The US navy had submarine tenders (supply ships, nod to justCal's comment) which could supply submarines at sea, which opens up the possibility of greatly increasing the aforementioned period of 75 days for some US subs. The Germans also had at least one submarine tender, the SS Saar, which was operational throughout the war. Thus, submarine crews could have remained at sea for extended periods during WWII without being able to set foot on land for some R & R.
What is the most number of days that a submarine remained at sea during WWII without going to a port to be resupplied (but which may have been resupplied at sea by supply ships)?
Also, were there any submarines of other navies (British, German, Japanese, Russian) which could stay at sea longer than this (75 days) without being resupplied? By 'could', I mean under relatively normal operating conditions (i.e. without the crew resorting to such extreme measures as drawing of straws / cannibalism, as suggested by Scott's comment).