I know most of you will find it hard to believe, but we are about to celebrate our 35th Anniversary.
( ( ( ( ( I ( know ( ( most ( of you ) ) ( will ( find ( it ( hard ( to believe ) ) ) ) ) ) ) ) , ) but ) ( we ( are ( about ( to ( celebrate ( our ( 35th Anniversary ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP I)) (VP (VBP know) (SBAR (S (NP (NP (JJS most)) (PP (IN of) (NP (PRP you)))) (VP (MD will) (VP (VB find) (S (NP (PRP it)) (ADJP (JJ hard) (S (VP (TO to) (VP (VB believe)))))))))))) (, ,) (CC but) (S (NP (PRP we)) (VP (VBP are) (VP (IN about) (S (VP (TO to) (VP (VB celebrate) (NP (PRP$ our) (JJ 35th) (NN Anniversary)))))))) (. .)))
It is the 40th anniversary. 
( It ( ( is ( the ( 40th anniversary ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (NP (DT the) (JJ 40th) (NN anniversary))) (. .)))