The Lord spoke to Moses, saying, "Speak to the people of Israel and say to them, These are the appointed feasts of the Lord that you shall proclaim as holy convocations; they are my appointed feasts." (Vayikra / Leviticus 23:1-2; ESV)
As far as I know every culture has special occasions that help define that particular culture. Feasts, festivals, and holidays provide people with collective memory and shared values. The western world, which has become more distanced from its religious past, has either redefined its religious holidays, such as Christmas and Easter, or has created new ones, such as Earth Hour and the Super Bowl.
The culture of ancient Israel as designed by God includes key events described in this week's Torah portion. These "feasts of the Lord" are the weekly Shabbat (English: Sabbath), the day of rest; the night of Pesach (English: Passover) followed by the week-long festival of Matzah (English: Unleavened Bread), commemorating the exodus from Egypt; the day of Shavuot (English: Weeks), which acts as the anniversary of the giving of the Ten Commandments; Yom Truah (English: Day of the Blowing of the Shofar), used to mark the New Year and prepare the people for the next two holidays, which are Yom Kippur (English: Day of Atonement), the national day of humility and repentance and the week-long Sukkot (English: Booths), to remember the days of Israel's living in the wilderness prior to entering the Promised Land. These occasions include prescribed sacrifices and gatherings of the people. Pesach, Shavuot, and Sukkot were also harvest festivals, requiring pilgrimage to Jerusalem each year.
These special days and observances gave Israel a sense of national community, caused the people to remember its history, and draw the nation's attention to God. The weekly Shabbat observance and yearly holy days provided a regular rebooting of Israel's awareness of who they were and what life is truly all about. To neglect these days would lead to a loss of identity and direction.
For many in the Jewish community today these and other special occasions continue to act as community identifiers. For some Jewish people, Judaism may have no other practical application apart from one or more of these days. The more religious within the community hold to the misconception that by observing these and other special days, they are preserving an unbroken line from Moses until now. I use the word "misconception," because the inability to offer sacrifices due to the Temple's destruction two thousand years ago makes truly keeping these God-given feasts impossible. Like much of Judaism since then, feast observance is a mixture of things reminiscent of Temple days and a great many man-made traditions. Differentiating between God's directives and human tradition would make these observances that much more meaningful and beneficial.
As Jewish followers of Yeshua, my family and I seek to continue our people's traditions albeit through a biblical filter. We acknowledge the feasts as part of our history and seek to discover the essence of God's intentions in these special occasions as expressed in Scripture, engaging in those things that are truly biblical and distancing ourselves from those things which are not. While we cannot actually observe the feasts as God intended, like the rest of the Bible, they contain essential aspects of God's revelation.
More and more Christians have become interested in the feasts. Recovering the biblical roots of New Testament faith is essential to understand what the coming of the Messiah is all about. The reality of the God of Israel can only be known within the context of his revelation through the whole Bible. But as for the feasts themselves, they can no longer be truly observed due to the Temple's destruction. Still, studying them and engaging in activities designed to teach the truths of God as revealed through them can be most worthwhile.