Leviticus 23 The Lord gave Moses a yearly timeline of feasts and assemblies for Israel. 

Every week, on the 7th day, was the Sabbath.  A holy day.  A day of rest.  A day of no work.. "a day of sacred assembly".  

Then... these appointed times.. feasts to the Lord. 

1st month -14th day:  The passover. 

1st month-15th -21st day: The Feast of Unleavened Bread.  A sacred assembly on the 15th and another on the 21st.  A food offering by fire every day of that week. 

Verses 10-14 describe a special ceremony for the "first fruits" of the harvest. Whether this is at a separate time or during the Feast of Unleavened Bread is debated by scholars.  On the first day of the harvest, they were to bring a sheaf of barley to wave before the Lord. They also brought a one year old lamb without defect for a burnt offering. Adding to this would be a grain offering together with some wine.  Until this offering was made the people were not to eat any of the newly harvested grain. 

7 weeks  (7 sabbaths) after the wave offering.. on the 50th day they were told to present a new grain offering.  This included 2 loaves of bread, ( with leaven) as a "first fruits to the Lord".  Added to this was 7 one year old lambs, a bull, and 2 rams;  one male goat for a sin offering; and 2 more lambs for a peace offering.  The bread and the 2 lambs were given to the priests.  There would be a holy assembly on that day. 

The next festivals would be during the 7th month. 

The 1st day trumpets would announce a "holy convocation".  No work could be done and offerings were presented. 

The 10th day was the Day of Atonement.  "it shall be a holy convocation for you, and you shall humble your souls and present an offering by fire to the Lord."   The people were called to humble themselves or be "cut off from his people."  They could do no work.  It was a day of complete rest and humble souls starting on the evening of the 9th day until the evening of the 10th day. 

On the 15th day the Feast of Booths began with another holy assembly. 7 days of offerings were followed by another holy assembly.  This was a time of gathering to celebrate the harvest. During this time they would gather branches of palm trees and "beautiful trees" like the willows.. and rejoice before the Lord in the booths that they made with these branches. This was to remind Israel of how God brought the people of Israel out of Egypt. 

Some believe that these appointed festivals preview the life of Christ.. The passover, of course,  points to His sacrifice as the perfect Lamb of God. The presentation of the first fruits points to the resurrection of Jesus as the "first fruits" of those who will be resurrected on the day He returns.  The seven weeks feast points to the day of Pentecost and the coming of the Holy Spirit.  Then there is a gap in the Jewish calendar until the 7th month. ( perhaps these years since Christ ascended into heaven). After this begins a new era.. with the sound of trumpets, then a period of humble repentance.. for atonement.. followed by the "ingathering".. a celebration of the final harvest of the year.. pointing to the return of Christ and the gathering of all believers into His eternal kingdom. 

Father in heaven, once again we rejoice in Your goodness and mercy upon us. We are so thankful for the salvation that we have through the atonement that Jesus made for us.  We come before You to humble ourselves.  We put aside everything else to worship before You. Our hearts yearn for that trumpet to sound and for Christ to come.. and we pray that we will be ready.. that our children will be ready.. that Your church will be ready for that great day.  Lead us Holy Spirit into true sabbath rest.. to be a holy assembly before our Lord... prepare us for that Day..  We ask this in Jesus' name. amen