Today is the first day of the year on the Gregorian Calendar and the first day of 2015 according the Anno Domini reckoning of years.
Of course, a “New Year’s Day” is an arbitrary notion and is celebrated at various times according to the traditions of different religions, cultures and nationalities. January 1st was adopted as the start of the year sometime during the era of the Roman Empire. During the Middle Ages, most European countries celebrated the New Year in the Spring. However, by the time the Gregorian Calendar began to be adopted by most Western nations, January 1st became the standard for celebrating the New Year.