"the company's 12/28 announcement stated 1/17 as ex date"
No, it didn't. Read it again: "The distribution is payable on February 4th, 2013 to shareholders of record at the close of business on January 17th, 2013."
Just where, exactly, do you read any mention of the ex-date?
The 17th is the record date, not the ex-date. That's why it says, "to shareholders of record at the close of business on January 17th, 2013." Nowhere in the press release is the ex-date even mentioned. A record date of Jan 17 makes the ex-date Jan 15th. To be a shareholder of record on the 17th, you would have to buy the stock no later than the 14th. That's why the 15th is the ex-date.