Vayikra (Leviticus) 23 is all about Elohim's Calendar. Here is what it says about the Holy time of Sukkot...
39 "'... on the fifteenth day of the seventh month, when you have gathered the produce of the land, you are to observe the festival of Yehovah seven days; the first day is to be a complete rest and the eighth day is to be a complete rest. 40 On the first day you are to take choice fruit, palm fronds, thick branches and river-willows, and celebrate in the presence of Yehovah your Elohim for seven days.
41 You are to observe it as a feast to Yehovah seven days in the year; it is a permanent regulation, generation after generation; keep it in the seventh month. 42 You are to live in sukkot for seven days; every citizen of Isra'el is to live in a sukkah (a temporary structure), 43 so that generation after generation of you will know that I made the people of Isra'el live in sukkot when I brought them out of the land of Egypt; I am Yehovah your Elohim.'"
Are you a citizen of Israel? If not by birth, Ephesians 2 says "11 Therefore, remember your former state: you Gentiles by birth - called the Uncircumcised by those who, merely because of an operation on their flesh, are called the Circumcised -12 at that time had no Messiah. You were estranged from the Commonwealth of Isra'el. You were foreigners to the covenants embodying Elohim's promise. You were in this world without hope and without Elohim.13 But now, you who were once far off have been brought near through the shedding of the Messiah's blood.