God's Appointed Days

The fact that the death and resurrection of Jesus and the outpouring of the Holy Spirit coincided with Jewish Old Covenant Feasts, is evidence that Jesus is the Messiah and that the Gospel fulfilled the Promises and Prophecies.  

But with the coming of the New Covenant, it was no longer necessary for Jews to continue keeping the Feasts. Therefore it wasn't necessary for Gentiles to begin keeping the Feasts. (And from about AD70 onwards it became impossible for anyone.) Christians experience daily what the Feasts could only foreshadow.

Perhaps we may be led by the Holy Spirit  to especially appreciate certain aspects of our relationship with God which fulfil a former Jewish Feast, on days which either knowingly or unknowingly to us coincide with the former Jewish Feast day. But that doesn't mean we're literally keeping the Feast. Paul talked about "keeping the feast" through a daily lifestyle, but never urged literally keeping the Feasts on their set days. It's been impossible for anyone to anyway, since about AD70.  

All Paul taught about any day, apart from the coming Day of the Lord, was that today is the acceptable year of The Lord, now is the day of salvation. This era is called Today.