What happened

Car rental giant Hertz Global Holdings (HTZG.Q) reports its fiscal Q2 earnings numbers on Monday after market close.

No, not today. Next Monday after the close. And that means that the 10.5% pop in share price that Hertz enjoyed today had nothing to do with earnings. To figure out why Hertz is up (still 6.2% as of 3:15 p.m. EDT), we'll need to look for another explanation.

Car Rental sign seeming to point up

Things could be looking up for car rental stocks. Image source: Getty Images.

So what

Luckily, I think I've found it. This morning, analysts at Northcoast Research announced they're upgrading shares of -- again, not Hertz -- but rather its rival Avis Budget Group (CAR 0.66%), which also reports earnings next week. Avis Budget shares suffered a steep drop late last month after being downgraded by analysts at Morgan Stanley, and are down about 19% over the past six weeks. According to Northcoast, that decline in share price created an "opportunity" to buy Avis stock on the cheap ahead of earnings, as Northcoast explained in a note covered on StreetInsider.com today.

But here's the thing: Simultaneously with Avis, Hertz stock also dropped last month -- and its shares are down 26%, even though Hertz wasn't the stock that got downgraded!

Now what

That fact may be leading investors to believe that Hertz stock was unfairly punished. They may also be thinking that if things are going right for Avis, they might also be going right for Hertz. That would raise the chances that the stock will succeed in cutting its losses from $0.63 a share (in last year's Q2) to $0.25 (in this year's Q2), as Wall Street has forecast,  when it reports earnings on Monday.

But just to be clear again: That's next Monday, not today.