Don't have build dates, but I think the S we bought in March 2017 was fairly new to the dealer. The replacement SL was purchased in February 2016, so one of the earlier ones manufactured in that model year I assume. Carfax on it doesn't list manufacture date - odd.
We purchased our 2016 Leaf S with the 30kWh battery in March 2017 and loved it (honestly beyond reason - and I'm not even a car person). Unfortunately, my husband was in an accident earlier this month that totaled it (without hurting him beyond a seatbelt burn and bruised shins, thank God)...