Romans 14:5
One man esteemeth one day above another; another esteemeth every day alike. Let every man be fully persuaded in his own mind.
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.
Rom 14:3 Let not him who eats despise him who does not eat, and let not him who does not eat judge him who eats; for God has received him.
Rom 14:4 Who are you to judge another's servant? To his own master he stands or falls. Indeed, he will be made to stand, for God is able to make him stand.
If you want to esteem that you can eat vegetarian on certain days feel free. I won't stop you.
But if you think Paul is suggesting that he didn't give a rip about the 4th commandment or the holy days of Jesus Christ then you're embracing Roman heresy and tradition.