According to holidayscalendar.com ...

"Although some people call any sparkling wine champagne, the truth is that [name is reserved for] only wines produced in the wine region of France called Champagne and it has to be produced using the rules of the appellation. It’s also a wine that can only legally use one of eight different predetermined grape varieties to be able to be called Champagne. That makes true Champagne quite a bit different than sparkling wines produced elsewhere. How different? The best way to find out is to try out some Champagne for yourself. And you might as well do it on December 31st—a day that is known not only as New Year’s Eve but also National Champagne Day."