If food laws can be a source of disruption in a local church, so can holy days — and it is not clear (according to Wright) if the holy days are Christians wondering if they should participate in Roman holy days or whether they should participate in Jewish holy days. The point for Paul transcends:
Each person must be convinced in his or her own mind — and that is enough.
And, let each person make their choice on the basis of honoring the Lord.
And, if the issue is a tolerable Christian difference, then when folks are personally convinced of their decision and when they do so in honor of the Lord, then let them do as they choose.
Now, of course, for some this opens the door to nonsense. And of course Paul assumes that individual Chrisitians have done their homework and are seeking to honor the Lord, and if they are responsible, then leave them alone.