Hi Scott:
Honda mowers don't use model years. They have a "version number" that is called a K-code that is part of the model number.
Some K-codes can be in production for years. Recently, certain model mowers were getting a new k-code every 12-14 months.
For your mower, the digit before the VKA tells me the K-code; your HRR is a K6 model, probably built 5-7 years ago. The most current K-code for the HRR is a K9. Here's the rest of the decoder ring:
HRR2166VKA
HRR = Honda HRR series rotary mower
21 = 21" cut
6 = 160cc displacement engine
(k)6 = K6 version of this model (K is understood but not printed/included in all model names due to system limitations)
V = SmartDrive
K = Flywheel brake (blade and engine start/stop at same time)
A = USA spec model (as opposed to "C" for Canada model)