Actually, that's correct.
If the period is part of the quote (ie- the quote ends at the end of a sentence) you put it inside the quote, otherwise, it goes outside. The only modification permissible to the inside of the quote is that a period in the quotation must become a comma if the end of the quotation doesn't end the containing sentence, or a comma must become a period if it will also signal the end of the containing sentence.
At least, that's how I was taught to do it.
George Bush said, "You've got 48 hours to get out of Dodge, Saddam."
"You've got 48 hours to get out of Dodge, Saddam," said George Bush.
George Bush gave Saddam "48 hours" to leave the town of Dodge.
Saddam has "48 hours to get out", according to Bush.
Bush gave Saddam "48 hours to get out of Dodge."
Bush told Saddam to leave within "48 hours".
I hope that gives a general idea...
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