Romans 14 has nothing to do with holy days. The greek text doesn't mention "holy" or "sacred" in any verses. The greek word for the holy days of the Lord, heorte (transliterated), is not mentioned here at all. In context this verse is referring to eating practices. It's most likely referring to a problem in the early church where clean animals had been sacrificed in pagan worship and later sold in the meat market. The issue as that early Christians were conflicted on whether they could eat meat that had been sacrificed to idols. Some became vegetarians. The "days" were likely those days that pagans sacrificed and put their meat out in the market.
Sorry if it seems I'm being a stickler about this but I am defending God's word. These verses have been twisted by others for over a thousand years to try and abrogate the word of God.