vin decoding for build

Im trying to find out the build date of Leaf's to see if they are post 4/2013. I'm looking into getting a 2013 SV or SL to keep costs down but also make sure the car has the newer heat resistant battery pack as users suggest in this forum for post 4/2013 builds. Since I'm in TN, I dont have physical access to the cars and most of my car research is online via dealer websites.

Some websites suggest that for Nissan, the VIN's 10th digit is the year and 11th is the month.
D = 2013
C = December

So for this vin XXXXXXXXXDCXXXXXX, does this vin number indicate a build date of December 2013 or am I completely off ?
A complete carfax report is the best way to get the build ?
If this is indeed the right build date should it be fair to assume that the car has the newer heat resistant battery pack?

D = 2013
C = December

Regards,
John

apparently the 11th digit in my case its "C" stands for the plant code which is TN.

John.

So now the questions is, how would I know the build month and date using the vin number so I know its post 4/2013?

John.