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Jan. 9: The stock passes $30 for the first time since July after Facebook sends out invitations for a mystery event that later turns out to be the unveiling of a new search feature.

Wednesday: Facebook reports fourth-quarter earnings that exceed Wall Street’s expectations. Its stock price fluctuates sharply in after-hours trading, as investors weigh lower net income and growing expenses against an increasing user base and higher advertising revenue. Amid worries about its ability to make money from mobile apps, the way more users are accessing Facebook, the company discloses that it generated 23 percent of advertising revenue from mobile, up from 14 percent in the third quarter.