Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of J.C. Penney (OTC:JCPN.Q) rose nearly 20% Wednesday after the company provided preliminary numbers on its holiday sales.

So what: For the combined nine-week November and December period, J.C. Penney reported comparable-store sales growth of 3.7%, year over year. Consequently, the retailer now expects fourth-quarter comparable-store sales growth to arrive at the higher end of its previous guidance range of 2% to 4%.

"Customers clearly responded to our combination of great merchandise and compelling promotions this holiday season," said J.C. Penney CEO Myron Ullman in a press release. "We are proud of these results, and believe the work we are doing will fuel the continued growth of our business." 

Now what: You might recall that almost exactly a year ago, shares of J.C. Penney plunged after it issued a brief, vague press release merely stating it was "pleased" with its holiday period performance. Shares were down about 20% since then going into yesterday's close, but investors today showed clear appreciation for the added details and effective guidance increase.

Even with today's pop, I'm personally just fine staying on the sidelines until we see J.C. Penney's full fourth-quarter results next month. But it's also hard to blame anxious J.C. Penney investors for celebrating today's good news.