It can only be used correctly for this purpose. It's going to be a beautiful day. Its beauty lay in its simplicity. Punctuation and Quotations Periods and commas always go inside the closing quotation marks.
Exclamation marks go inside quotation marks.
Colons and semicolons go outside of quotation marks. In a sentence, a quotation is preceded by a comma unless the introductory phrase is very formal, ending in words or phrases like thus or the following . In such cases the quotation is preceded by a colon. Also, a sentence which introduces a block quotation ends with a colon. Commas after Introductory Phrases These are usually followed by a comma, unless the phrase is very short.