5 Dates to Circle in May

May is here, and it's time to make the "sell in May and go away" purists jealous.

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

May 5
All eyes will be on Omaha this weekend.

The annual Berkshire Hathaway (NYSE: BRK-A) (NYSE: BRK-B) shareholder meeting takes place on Saturday.

Beyond six hours of brain-buzzing Q&A, subsidiary discounts, and value investors high-fiving one another, this get-together will be different.

Ever since Warren Buffett revealed that he has prostate cancer, investors have been right to question the mortality of a man considered by many to be the greatest investor of our time. The Oracle of Omaha isn't worried. He's confident that the cancer was diagnosed early enough to be tackled effectively.

However, you can be sure that questions of succession will come up. Buffett is 81 years old, and Charlie Munger is also getting along in years.

There will also undoubtedly be a lot more applause than usual. You just never know when it will be Buffett's final Berkshire Hathaway meeting, and he's certainly more than worthy of the accolades.

May 9
For a brief moment in time -- before the dot-com bubble popped -- Cisco Systems (Nasdaq: CSCO) was the country's most valuable company by market capitalization. Everyone was going crazy about networking and going online, and Cisco was there with the networking routers and switches to make it happen.

Things haven't gone so well for Cisco since then. The recession obviously slowed IT spending, but Cisco also stumbled in the consumer market. Competition has also been fierce, driving down margins.

Cisco reports next week, and things are starting to look up. Analysts see revenue and earnings climbing 7% and 12% higher, respectively.

May 14
Howard Stern is now two weeks away from his primetime debut on NBC's America's Got Talent. A controversial radio show host ready to skewer talent show contestants may not seem like investable news, but try telling that to Sirius XM (Nasdaq: SIRI) shareholders.

Stern was suing his radio company -- alleging that Sirius XM owed him stock rewards for the subscribers that the company gained when Sirius merged with XM -- until last month when a judge dismissed the lawsuit. Stern's camp moved to appeal the decision, but now we're up against a primetime show that should make Stern even more marketable.

Can Stern and Sirius XM both prosper even when they're at each other's throats?

May 17
Barring a general market collapse or any hiccups on Facebook's part, the world's largest social networking website will go public this month.

A source originally told CNBC that Facebook was targeting either May 17 or May 24 to make its trading debut, but last week several reports claimed that Mark Zuckerberg's dot-com darling is eyeing May 17 as the date.

Between Facebook's registered user base of roughly 900 million people and the $100 billion valuation being tossed around, this would be a tech IPO for the ages. Expect a lot of investors to click the "Like" button on this one, until they sober up to the whopping valuation.

May 24
Costco (Nasdaq: COST) reports toward the end of the month.

Why should investors be paying attention? The warehouse club has been one of the market's most consistent performers over the past two decades. The recession-resilient nature of warehouse clubs and Costco's sharp execution and expansion have made the stock one of the market's biggest winners.

Well, popular CEO Jim Sinegal retired in January. This will be the company's first complete quarter without Sinegal at the helm. There shouldn't be any surprises, but it will be notable for his absence.

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