A few months ago, I received a card titled "Here's to another Rewarding Year", telling me I have a free night's stay. It says it will be posted to my account 6-8 weeks after my anniversary date, but I do not find any information as to how to redeem, where to find my anniversary date, or the period for which it is valid. Where do I find this?
If it's posted to your account already, you should see it under "Unused Rewards Certificates" under My Account:
Do you have the Marriott Credit Card? Other than that, you usually need to earn those free nights during a promotion. Either way, it should be in the above link unless it hasn't posted yet.
You have two ways to redeem the free night. First method is to just call the Marriott reservation line and tell them you want to use the free night and which date you want. You can also do this during the reservation process. I don't remember the exact details when I last did it, but there is an option for you to select to use the free certificate. See below for more details from another topic with a similar question:
AS for your 2014 enquiry... In common with many Internet forums, and particularly those related to travel such as Flyertalk and Milepoint, the forums are open to view, but only members have posting privileges...