Call me any time after 12pm.
Call me anytime after 12pm.
Are both sentences grammatically correct and mean the same thing?
I looked into their differences, and there aren't any, other than how it is any time that is always used with prepositions. If I'm not wrong, both sentences are correct and acceptable in formal writing.
The single word “anytime” is a fairly recent addition to standard English. It should only be used as an adverb, and it would not be appropriate in formal writing.
The phrase “any time” can be used wherever “anytime” can be used, and in a lot of contexts where “anytime” cannot. The easiest path is to write it as two words. If you want to use “anytime” informally, I don’t think any mistakes you make using it will be obvious to most people, or judged harshly by those who do notice.
For your specific example,
Call me any time after 12pm.
is correct. If you wanted to use “anytime”, you would write:
Call me anytime, as long as it’s after 12pm.
This article on ThoughtCo has a lot more detail, and includes this helpful summary:
- "Any time" can function as either a noun phrase or an adverbial phrase.
- "Any time" is always correct.
- "Anytime" is always an adverb.
- "Anytime" cannot follow a preposition such as "at."
- Use "any time" when referring to an amount of time.
- Never use "anytime" in formal writing.
The correct sentence is
Call me any time after 12pm. (where time is used as a noun)
If you wish to write anytime, you must use it as an adverb:
Call me anytime (whenever).
See this explanation from the site Thoughtco:
The word "anytime" is a contraction known as a casualism, which is the result of the informal usage of a grammatically incorrect word becoming widely accepted. "Anytime" is an adverb meaning "whenever" or "without a doubt." It is only correct when used as an adverb. Examples include:
- You can call me anytime.
- The boxer said that he could defeat his opponent anytime.
Here is an example of incorrect use:
Incorrect: The smoking volcano could erupt at *anytime.
