Ehh... New year's was three and a half months ago...
In fact the year of the Creation of the world was in Rosh Hashanah, and it applies also to Gentiles (but they must not do the Jewish rest).
However the Gregorian Calendar has been accepted by many Gentiles and even some Jews in the Diaspora for practical reasons. Jan 1st was a civil New Year in Rome before Christianity, when Julius Caesar adopted a version of the Egiptian calendar. So it can be considered a neutral civil holiday and there's nothing wrong with it. (however a Jew should consult his Rav)