While He walked on earth, I think that would be the Jewish ones, the ones before the Messiah was the passover sacrifice, before our Saviour's death and resurrection.
Is this where you wish to freeze His Church, and its religious observance? To the point before His sacrifice, before the Lamb of God? Freeze history here and there is no passion, sacrifice and resurrection of Christ and no future of the His Body.
Better to ask "What Religious Days Does the Body of Christ Observe?"
If God's holy days were observed without the truth or understanding that the messiah has come and will return then I might agree with you.
The holy days actually shadow and portend significant events for Judaism and Christianity.
For example, Passover represents the death of Christ on the cross:
1Co 5:7 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:
The Days of Unleavened Bread represents the life of a person after accepting Christ. The physical act of removing leavening represents and reminds us of the spiritual attitude of removing sin from our lives. Examining ourselves for sin (leavening) and removing it from our lives.
Another example: The Feast of Trumpets (Rosh Hashanah) represents the 2nd coming of Christ, at the last trump:
Rev 11:15 And the seventh angel sounded (his trumpet); and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever.
1Co 15:52 In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
1Th 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
I hope that helps. For further reference, see God's Holy Day Plan.