Leviticus 23

"‘These are the feasts of the Lord, holy convocations which you shall proclaim at their appointed times.  On the fourteenth day of the first month at twilight is the Lord’s Passover...‘The fifteenth day of this seventh month shall be the Feast of Tabernacles for seven days to the Lord."  vv.4-5,34

Read chapter 23.
In the U.S there are 11 Federal holidays with many many many other holidays observed by different religions, diversities and agencies each year.  In scripture we also see many holidays or feast set by the Lord (*note Christmas is not one of them).  There are six Feasts listed in this chapter (seven if you count the weekly Sabbath).  Each has it's specifics for reason and how to observe that holiday. Just like many holidays celebrated to day, the Israelites were to do no customary work on these holidays.  They range from the first month to the seventh month of the Hebrew calendar.  The first of the feasts mentioned is the Passover about redemption and the last is the feast of Tabernacles about rest.  In order to have rest you need redemption.  These feasts are not commanded to be celebrated today by believers, and some couldn't be as they were specific to Israel and not gentile believers.  We may celebrate our own holidays for what God has done as remembrance to us.  How have you seen holidays that were created to honor God change its focus to something other than?