Trek stopped making the T900 several years ago. You can tell what model year your bike is by looking at the last letter in the serial number printed on the frame near the bottom bracket.
I found another thread on here that talked about a recall bulletin from Trek which explained the final serial number character of "D" represents the 2009 model year. Going forward from that (and skipping "I" and "O" as many manufacturers do because they look too much like 1 and 0),
D - 2009
E - 2010
F - 2011
G - 2012
H - 2013
J - 2014
K - 2015
L - 2016
M - 2017
N - 2018
P - 2019
Q - 2020
R - 2021