Jesus came to us as a Jew (Hebrew) and respected the foundation of the Old Covenant and established the New Covenant upon that foundation. Matthew 5:17 "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them". If we are not building our Christian Faith upon the foundation that Jesus laid, then we are building on an inferior foundation.
Jesus is the fulfillment of the law. God made sure that the old covenant sacrifices could not continue when He allowed the Temple to be destroyed in 70 AD. However, God's Appointed Times and Seasons still stand as a reminder of a Divine Prophetic Plan for the redemption of humanity. Replacing God's Holy Times, that are rich in prophetic history and the discriptions of future events written into the the DNA of the Hebrew calendar is dangerous. It's dangerous because we don't have the authority to change or replace the things of God. This behavior shows a tremendous lack of respect and lack of spiritual discernment for the sacred.
There are four Spring moedim that has been fulfilled in the life of Yeshua.
Passover – Pesach
Feast of Unleavened Bread – Matzah
Feast of First Fruits – Yom Habikkurim
Feast of Weeks (Pentecost) – Shavuot
The Fall moedim are yet to be fulfilled by The Return Of Christ’s. This is one of the reasons we anxiously await His Return.
Feast of Trumpets – Yom Teruah (Rosh Hashanah)
Day of Atonement – Yom Kippur
Feast of Tabernacles – Sukkot
The Hebrew Root Of Christianity:
There are eight “Appointed Times Of Our Heavenly Father” in Leviticus 23. The very first moed (singular of moedim) is mentioned as the weekly sabbath.