I have J deere l120 serial gxl120 a099604 what year is it thanks

Hi,
The answer is at JDAnswers under the model reference for the 2000's. It is a 2004 model. This reference can be found at:
BSM-1401091MA
Om page 2 in the right hand column.
Incidentally, I am glad glad you capitalized the L in the heading since Deere also made an 1120 compact utility tractor, which I did not find the year for.
Peace,
Clarke