if this sentence use for expressing the mood.you may say,"meihao de yi tian "(美好的一天）or" feichang bang de riji"“非常不错的日子”;
if use it to express the wether,you may say "tian qi bu cuo"（天气不错）or "yang guang ming mei de yi tian" （阳光明媚的一天）or "qing gao qi shuang "（清高气爽）.all these the simple mean is "tian qi hen hao"(天气很好）。
i think a sentence has many means, it depends on your language circumstance.
