I’m retired and plan to attend a formal New Year's Eve event. Is it acceptable to wear my dress blues?

LTC Walter Wilson, I must agree with CSM Darieus ZaGara Chapter 23 of AR 670-1 states that the uniform may worn on occasions of ceremony and the event you have described does not meet the definition. In my opinion, it’s not really a gray area.
“As used in this regulation, the phrase ‘occasions of ceremony’ means occasions essentially of a military character, at which the uniform is more appropriate than civilian clothing. These functions include, but are not limited to: military balls, military parades, weddings, and military funerals; memorial services, meetings, conferences, or similar functions of associations formed for military purposes, of which the membership is composed largely or entirely of current or honorably discharged veterans of the Armed Forces of the United States. Authority to wear the uniform includes wear while traveling to and from the ceremony or function, provided the travel in uniform can be completed on the day of the ceremony or function.” SCPO Jason McLaughlin

Review AR 670-1 for your own interpretation. As I read it, I would not wear the uniform it is essentially a party and not a ceremonial type event. Thank you for your service.

No, my interpretation of AR670-1 unless it is hosted as a military event