Are you sure that 'early' is an adverb? It seems like an adjective in those phrases. Early是副词,a few hours early不构成词组,是中国式的英语。 请看下面两个例句: i came three hours earlier than the others.
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Hi, we all know that one month has three sections which are defined as early/middle /late +month, for example: 我比其他人早来三小时。 the ship arrived 30 minutes early.