Expression: "just got back to my office this AM"

[Tom]

Hello

Could you please tell me what AM means in the given expression?

"I have been away on business and just got back to my office this AM."

Tom

[Mister Micawber]

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AM = morning
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_________________
Native English teacher at Mister Micawber's

[Tom]

Thank you, Mr. Micawber

But doesn't AM consist of or mean "12 hours?"

So this AM could be any time from 12(night) to 12 (day)? Please answer.

Tom

[Mister Micawber]

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You asked what AM meant in this sentence, and I told you, Tom. You must use common sense when you try to interpret the very flexible English language. Standard office hours are 9-5, so he means that he came back to his office between 9 am and noon, or a reasonable facsimile thereof.
.
_________________
Native English teacher at Mister Micawber's