He literally spoke of regarding a Day... it is not just about eating...
In context it is about eating practices on specific days but NOT on the sabbath or holy days. And NOT worship days. There is NOT a word used in the greek to denote that these "days" are any type of worship days.
There was a controversy in the early church about buying and eating meat that had been sacrificed in pagan rituals and then sold in the meat market. This is touched upon in 1 Corinthians chapter 8.
Pagans would sacrifice an ox or goat in a ritual and then afterwards sell the meat at market to profit from it. Early Christians asked the question: Is that right? Should we buy and eat that? It seemed to be quite the controversy. Paul ultimately said it's just meat...but let your own conscience decide.
They knew which days the pagans put their meat out and so some people would refuse to eat or buy meat on those days. If they went to a friends and the friend tried to serve them meat they would refuse it if they suspected it came from meat market on those days of the week.
That's why Romans 14 starts off this way:
Rom 14:1 Receive one who is weak in the faith, but not to disputes over doubtful things.
Rom 14:2 For one believes he may eat all things, but he who is weak eats only vegetables
What traditional Christianity did with the verses in Romans 145-6 is to completely cut out all context and ignore the cultural wars going on in Christianity at the time.
Romans 14 is NOT about changing days of worship or sending the message that the day of worship is not important. What it's really about is not getting into these stupid disputes about whether or not someone was holier because they did or did not eat meat that had once been sacrificed to idols. It's a chapter devoted to Paul teaching the brethren about this issue and not to dispute about it.