彼は私より1年若いです is the best. 若い(わかい) means young
I can understand 彼は私よりいちねんはやいです.
In that cace, however, 彼は私より1年早生まれ(はやうまれ)です is the best.
2015년 4월 19일
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I would say:
彼は私より一歳年下です。(かれはわたしよりいっさいとししたです。)
I hope this was helpful.
2015년 4월 20일
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Ops sorry, you said "He", isn't.. So put 彼 (kare) instead of あなた.
2015년 4월 19일
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Hmm.. I think you could say
あなたは私よりいちねんはやいです。(anata wa watashi yori ichinen hayai desu)
りい is the particle making a comparasion between you and the person.
いちねんはやい means "one year less" or "one year younger".