When to Use Anytime (One Word)
Anytime, used as a single word, is an adverb, and it has a meaning similar to “whenever,” “at any time,” or “ on any occasion.”
作为一个单词使用时,anytime是一个副词,它的意思类似于“whenever(不论何时)”, “at any time(随时)”, or “on any occasion(在任何场合)”。

例:
If you have any questions, you can contact me anytime.
如果有任何问题,你可以随时联系我。
When to Use Any Time (Two Words)
Any time is a noun phrase, and it has a meaning similar to “any amount of time".
Any time是一个名词词组,它和“any amount of time”的意思一样。
Just like the one-word anytime, the two-word any time also functions adverbially, but it also has additional functions as a noun phrase.
就像单词anytime一样,两个单词的any time也有副词用法,但它除此之外还可以作为名词词组。

那么大家可能就会有疑问了,
既然这俩都可以作为副词,
那是不是就意味着他们可以互相替换呢?
其实并不可以
在我们在造句的时候,
尤其需要注意他们与介词连用时,
只有分开的两个词 any time 可以和介词连用,
举个例子:
I can hang out at any time tomorrow night. (CORRECT)
I can hang out at anytime tomorrow night. (WRONG)
因为介词后是不可以接副词的
大家在写作时一定要注意这些细节哦~