For purists, it's the turn of the "real millennium." For everyone else, it's an excuse to party. Revelers around the country geared up for New Year's celebrations Sunday, even as city officials worked to clean up messes left by uncooperative winter weather. Snow was cleared from New York City's Times Square on Sunday in preparation for more than 500,000 people expected to gather for the New Year's celebration watched by millions around the world. It won't be as big as the bash attended by 2 million people last year, but Mayor Rudolph Giuliani predicted that snow from a storm that swept through the Northeast on Saturday will make it "even more beautiful." Former heavyweight champion Muhammad Ali will press the button to start the descent of the 1,070-pound Waterford crystal ball that lights up at midnight. More than 6,000 police officers will be on hand, and manholes will be welded shut and trash cans removed as a security precaution. Meanwhile, America's official timekeeper, the U.S. Naval Observatory, plans to mark the new millennium accurately with a celebration for 3,000 people at its Washington headquarters. Under the widely used Gregorian calendar, which started with the year 1, the third millennium doesn't begin until Jan. 1, 2001. "Real millennium" bashes are also planned in Las Vegas and Denver to make up for fizzled celebrations last year. At least 100,000 people are expected for a fireworks extravaganza in downtown Denver. And Las Vegas plans to explode $500,000 worth of fireworks over the Strip to a crowd of 500,000, double last year's turnout. by The Associated Press