分析一下这个句子的结构

One important regulation主语
of the foreign study program介词短语作定语
has to do with 谓语
the time, 介词宾语
established by the host "parents", 过去分词短语作reglation的定语
by which the teenagers must arrive home on weekend nights.非限制性定语从句，先行词是time.

has to do with the time是说和时间有关, established by the host "parents"做定语，表示这种要求是由家长建立的, by which the teenagers must arrive home on weekend nights是定语从句，修饰regulation.

翻译：在国外，学习项目的一个重要规则是涉及到时间，这种规则是由家长建立的，根据这个规则，孩子在周末晚上必须要回家~