各位老师好，对于以下两个句的分词用有疑惑，分词的逻辑主语不是如果句子主语么？但这两个貌似不是：
1.Starting this month,however,users of WhatsApp will find it harder to spread content.
2.Come the holidays, they can suddenly find their schedules and budgets stretched.
是由于表示时间，所以逻辑主语可以不是句子主语么？而且为何一个用-ing一个用-ed分词？谢谢老师。
1 Starting this month,however,users of WhatsApp will find it harder to spread content.
目前分词短语不是修饰性状语，而是评注性状语，是说话人对句子内容的注解，即starting的逻辑主语为整个句子内容。等于：
It starts this month that users of WhatsApp will find it harder to spread content.
或者：
Users of WhatsApp will find it harder to spread content，starting this month.
Users of WhatsApp will find it harder to spread content, which starts this month.
2.Come the holidays, they can suddenly find their schedules and budgets stretched.
come在这里并非过去分词，而是动词原型式虚拟语气。动词原型倒装于句首，省略连词when. 此为古体使用方法（when从句表示以后用be式虚拟语气）。所以本句等于：
When the holidays come, they can suddenly find their schedules and budgets stretched.
《韦氏高阶》come此使用方法的例句如下：
The days will be longer when springcomes. =Comespring the days will be longer.
Shell be back in schoolcomeSeptember. = Shell be back in school when Septembercomes.
