The field is about 100 years old.
( ( The field ) ( ( is ( ( ( about 100 ) years ) old ) ) . ) )
(ROOT (S (NP (DT The) (NN field)) (VP (VBZ is) (ADJP (NP (QP (RB about) (CD 100)) (NNS years)) (JJ old))) (. .)))
The field is 2 years old.
( ( The field ) ( ( is ( ( 2 years ) old ) ) . ) )
(ROOT (S (NP (DT The) (NN field)) (VP (VBZ is) (ADJP (NP (CD 2) (NNS years)) (JJ old))) (. .)))