The Torah divides the calendar into two symmetrical halves: the Spring and the Fall, indicating the two advents of Messiah. The Biblical year officially begins during the month of the Passover from Egypt (i.e., on Nisan 1, called “Rosh Chodashim,” see Exod. 12:2), and the spring holidays of Passover, Unleavened Bread, and Firstfruits both recall our deliverance from Egypt and also our greater deliverance given by means of the death, burial, and resurrection of the Messiah, the great Passover Lamb of God: Yeshua was crucified on erev Pesach (during the time of the sacrifice of the Passover lambs), buried during Chag Hamotzi (the festival of Unleavened Bread), and was resurrected from the dead on Yom Habikkurim (the Day of Firstfruits). Fifty days after the Passover, on the climactic holiday of Shavuot (i.e., the feast of Pentecost), the wave offering was made at the Temple as the Ruach HaKodesh (Holy Spirit) fell on the believers in fulfillment of the promise given by our Lord.
Note that the giving of the Holy Spirit occurred precisely according to the calendar countdown given in the Torah (Lev. 23:15-16), and that it occurred after the resurrection of Yeshua — just as our Messiah foretold (John 16:7; Acts 1:6-8, 2:1-4). This proves that the feasts of the LORD (מוֹעדי יהוה) were not abolished after the institution of the New Covenant and the crucifixion of our Lord. The meaning of the gospel is prefigured in the holidays given in Torah. See Luke 24:27, 24:44; John 5:46; Acts 26:22, etc.
Kindly note that in accordance with both Torah and Jewish tradition, the holiday dates (shown in the table below) begin at sundown (Gen. 1:5).
For more see the Hebrew for Christians Holiday pages.