October is here, and the fourth quarter is going to have a lot to live up to after three surprisingly buoyant quarters.

Let's go over a few of the upcoming days to watch.

Oct. 10
Costco (COST -0.24%) hit a new all-time high last week.

That's not too shabby considering that longtime CEO Jim Sinegal retired back in January. If there were any doubts about an orderly succession at the time, they don't exist now. Costco has gone on to deliver better-than-expected quarterly results in the warehouse club's first two quarters under new helmsman Craig Jelinek, and it will get a chance to stretch that streak up to three when Costco reports next week.

Shares of Costco have climbed higher than 20% so far this calendar year, so the warehouse club should be in good shape.

Oct. 15
Apple (AAPL -1.22%) has yet to announce the release date of its fiscal fourth quarter report, but the country's most valuable company has historically posted its financials during the third week of October.

There's plenty riding on this report. The iPhone 5 hit the market toward the end of the reporting period, and investors will want to know how many handsets Apple sold beyond the original 5 million smartphones that were snapped up during the iPhone 5's first day of availability.

Oct. 18
It's time to get that burrito rolling.

Chipotle Mexican Grill (CMG -1.34%) reports on Oct. 18. Analysts see the fast-casual chain growing revenue and earnings by 19% and 21%, respectively, for its latest quarter. Yes, Chipotle used to be growing faster, but it's hard to expand at the same needle-moving clip once you have more than a thousand restaurants.

Investors will want to keep an eye on comps and margins. Store-level sales are important, and Chipotle has managed to grow its comps even during the darkest recessionary stretches. Margins will be the bigger challenge, as Chipotle and other eatery operators have to deal with fluctuating food costs that can't always be passed on at the cash register.

Oct. 23
Electronic Arts (EA 1.30%) hopes that diehard gamers are still trigger-happy when Medal of Honor: Warfighter hits retailers.

EA had aggressive plans for the combat franchise, even bragging two years ago about the highest pre-sales in the franchise's 11-year history. Unfortunately for the game maker, too many critics panned the game. Now this is just the filler that comes out a few weeks before a new Call of Duty installment hits the market.

Given the way that the video game industry has faltered over the past three years, EA -- and developers in general -- can use a hit. We'll see if EA can make the battlefield interesting again with the Oct. 23 game release.

Oct. 26
Microsoft (MSFT -1.27%) is betting plenty on Windows 8, the software giant's latest operating system.

Windows 8 is a bold redesign. It's Microsoft's first operating system coded with touchscreen tablets in mind. Mr. Softy realizes that tablets and smartphones are starting to replace casual PC usage, and it wants to make sure that it doesn't fall too far behind the more popular gadgetry being outfitted with Android and iOS.

This promises to be a busy week for Microsoft as it will also coincide with the first wave of Windows Phone 8 devices and the company's first foray into tablet hardware with the Windows-8-powered Surface.

Since Microsoft usually takes a couple of years between operating system updates, the critical nature of this release cannot be underestimated. The world's largest software company can't afford to come up short here, and perhaps that's why it's offering aggressively low upgrade pricing.

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