The first story of creation in the book of Genesis sets the creation of the world in a period of seven days. God did the work of creation in six days and then rested on the seventh. That seventh day (Saturday) became the basis of the Sabbath, the day of rest. Putting that creation in the framework of a week showed that God had a plan and that everything fits into His plan. For the Jews, then, the number seven came to symbolize completion.
And then came Christ, His death and resurrection brought an even greater completion to the plan of salvation. In fact, we learn to see that all of the Old Testament was in preparation for the salvation that Christ would win for us. His resurrection occurred on Sunday, which quickly became the Christian holy day. Most of the early Christians, keeping their Jewish roots, observed the Sabbath with the rest of their community and then gathered with those who saw Jesus as the Messiah on the day of Resurrection. The Church soon came to see Sunday as a fitting day for that greatest of all events. As the day on which creation began, the first day became an appropriate time for God to provide us with a new creation. So Easter becomes the first day of a “new week” by being the start of a new creation. Yet the new creation does not do away with the old. In fact, we come to see that the completion we understood in the Old Testament was truly a preparation for the real completion that Christ would bring. Thus, in addition to being the first day of a new week, Sunday also becomes the Eighth Day, the day on which God brought about a deeper reality to all of creation.
We get a similar image from the other meaning we give to the word “octave.” In music, an octave refers to the eight notes of the scale. For those who are not musically inclined, think of the song “Doe, a deer” from the Sound of Music in which Maria makes a pun on the names of the various notes: do, re, mi and so on. “Do” is the eighth note, but it is also the same as the first note. In returning to “do,” we are back at the beginning while at the same time being and octave higher.
So Easter is a return to the creation of the first day while being an entirely new creation. To emphasize that, the Church takes the entire eight days of the Easter Octave to show the new creation by keeping the celebration as one long Sunday, So again, rejoice. And I still wish all of you a very blessed Easter Sunday.