The verbs in the simple present tense in the sentence express ability
eg:-I believe I can climb AH
=AH will be climbed (by me)
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when May 16 ,Saturday, arrives
=adv.cl. of time and condition.
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Hence the sentence completes in the simple present tense as follows:-
=AH will be climbed (by me) when May 16 arrives.
=Apple Hill will be climbed when May 16 arrives.