Because of their smaller size, most keep hours that allow people to enjoy themselves, then have some quiet after midnight, as opposed to large major cities like New York, where the buzz of activity is ongoing.  

来自2017年12月六级英语阅读理解。

参考翻译给的是，由于这些城市比较小，大多数都会运转到让人们尽兴而归，然后在午夜过后享受一段宁静，而不像纽约这种大型城市，喧嚣从不间断。

主要是不知道这个keep hours that怎么理解，求教各位老师。