They usually start in August. Of course it is not set in stone, some years it varies.
For example, 2012MY updated LC/LX ( 2013 for US ) started production in January 2012.
2011 LC/LX started production in July 2010.
I think they switched over from 100 series to 200 series production in August 2007. I remember when i saw my first 200 in real life the production date was September 2007.
2006 LC100/LX with updated lights started production in April or May 2005 as i remember seeing the first ones on the road in June 2005 .
My vehicle is a 2015 LC and it was produced in August 2014, it left Japan on the 2nd of September. ( details on the factory paper in the windshield )
I could also tell from the VIN. Look at the 10th digit/letter in the VIN
F = 2015
E = 2014
9 = 2009
Y = 2000
you get the pattern...