Because it marks the first day of the New Year on the Gregorian calendar, just as the Fourth of July is on the Fourth of July in the US and the Winter Solstice is celebrated on the day of the Winter...
Yes, January 1st is a Holy Day, the Feast of the Solemnity of Mary. http://www.cptryon.org/compassion/mary/trad04.html
September 11th
New Years Day is January 1st.
Saturday.
New Year's Day - 10 Fun Facts
How to Make a New Year's Day Brunch
Southern New Year's Day Vegetarian Soup
Curvy Chloe Sevigny's Bikini Malfunction