One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind. 6 Whoever regards one day as special does so to the Lord. Whoever eats meat does so to the Lord, for they give thanks to God; and whoever abstains does so to the Lord and gives thanks to God. 7 For none of us lives for ourselves alone, and none of us dies for ourselves alone. 8 If we live, we live for the Lord; and if we die, we die for the Lord. So, whether we live or die, we belong to the Lord. 9 For this very reason, Christ died and returned to life so that he might be the Lord of both the dead and the living.
As we discuss debatable issues, if we're asking, "Is it OK?", we're probably asking the wrong question. Paul talks about doing things "to the Lord" in this passage which means to me, the question we should be asking is does this glorify You, Lord?"
Let's take two holidays Christmas and Halloween. We discussed Santa recently but if I ask the question "is it OK to put up Santa decorations?" and "Does it glorify God to put up Santa decorations?", I get two different answers. It's not a sin to celebrate Santa Claus but celebrating him does nothing to, in fact detracts from lifting up the incarnation of God, the real reason for the holiday. What about trick or treating? If we ask those two questions, in my opinion we get the same answer - yes. There is nothing against going door to door with your little kids dressed up like superheroes or princesses and it glorifies God spending time with your kids and meeting neighbors. A different issue would be decorating with witches, skeletons, etc. You could ask those two questions and also get the same answer - no.
This is the second rule for debatable issues - ask those two questions and if the answer is yes, then go for it. What's the first rule? If your brother or sister asked those questions and came up with a different conclusion than you, let God grow them. Or maybe you came up with the wrong answer. Look further into the issue and make sure your heart isn't hardened in this area. As a kid, Wizard of Oz showed once a year and it was always Sunday nights - church night. I remember asking my Dad if I could miss church just this once and he told me to go in the bedroom, get on my knees and pray about it. After several minutes I came out and said, "God says I can skip church just this one time." My Dad didn't say, "No He didn't!", but he let me stay home from church. He was allowing me to make the wrong decision on a debatable issue (morning AND evening church) because he was growing me to stand. It's complicated but we will keep exploring this issue.