The Feasts of YHVH are prophetic appointments that show us things about the Messiah. These are set apart times that the Father wants us to practice, so that we will be ready for the Messiah. This is the Creator's Calendar, and He has told us in advance what He plans to do, if we will follow His calendar, we will be ready for what He plans to do.
And YHVH spoke to Moses, saying, "Speak to the children of Israel, and say to them: 'The Feasts of YHVH, which you shall proclaim to be holy convocations, these are My Feasts. (Leviticus 23:1-2)