By Anne D'InnocenzioNEW YORK -- Put down that turkey leg. It's time to shop. No, really. Stores typically open in the wee hours of the morning on the day after Thanksgiving known as Black Friday, named for the period when stores traditionally turn a profit for the year. But Black Friday openings have crept earlier and earlier over the past few years. Now, stores from Wal-Mart ( WMT) to Toys R Us are opening their doors on Thanksgiving evening, hoping Americans will be willing to shop soon after they finish their pumpkin pie. Wal-Mart Stores Inc. will have early bird shopping specials at 8 p.m., two hours earlier than a year ago. Target Corp. ( TGT) is opening its doors at 9 p.m. on the holiday, three hours earlier than last year. Sears ( SHLD), which didn't open on Thanksgiving last year, is opening during from 8 p.m. and will stay open until 10 p.m. on Black Friday. And Toys R Us will be opening at 8 p.m., an hour earlier than last year. It's an effort by stores to make shopping more convenient for Americans, who still face economic uncertainty. Many shoppers are worried about high unemployment and a package of tax increases and spending cuts known as the "fiscal cliff" that will take effect in January unless Congress passes a budget deal by then. At the same time, Americans have grown more comfortable shopping on Web sites such as Amazon.com ( AMZN), where they can get cheaper prices and buy from the comfort of their home or office cubicle. That has put pressure on brick-and-mortar stores, who can make up to 40% of their annual revenue during the two-month holiday shopping season, to compete. That's becoming more difficult: the National Retail Federation, an industry trade group, estimates that overall sales in November and December will rise 4.1% this year to $586.1 billion, or about flat with last year's growth. But the online part of that is expected to rise 15% to $68.4 billion, according to Forrester Research.