Employment Law Questions? Ask an Employment Lawyer.
what outcome are you seeking at this point and what may I answer?
Your union contract would cover holidays. You want to see that for definitive answer, specific to your employ. Normally, employer can require holiday work but has to compensate at additional rate. The union though may have negotiated certain days and terms.
I will opt out since I do not have the specific contracts and perhaps someone else has that information available.