Many of us have heard the term, “Pentecost,” but what, exactly, is it? Some confusion may be natural because the term has several meanings.

Originally, Pentecost was a Jewish holiday, one of the three pilgrimage festivals in which every Jew who could was required to come to the temple in Jerusalem and present their offerings to God. Specifically, it was the first fruits of the wheat harvest. In Judaism, it was known as the “Festival of Weeks,” or in Hebrew, Shavuot. Because it fell on the 50th day after the festival of Passover, the Greek term, “Pentecost” or “fiftieth day,” came to be applied to it.

After the death and resurrection of Jesus, the book of Acts tells us that the disciples were told to wait in Jerusalem until they should receive “power from on high.” This was fulfilled at the temple on the day of Pentecost as the disciples joined other Jews in celebrating the festival.

The Book of Acts tells us that it was there that the Holy Spirit descended on the disciples “like tongues of fire” and they were able to be understood by all there in their own language, reversing the confusion of languages that resulted from the Tower of Babel story. Peter’s speech at Pentecost says that this was a fulfillment of what was spoken by the prophet, Joel, when it was foretold that God would pour out the spirit “on all flesh.”

In Christian tradition, the day of Pentecost is traditionally understood to be the birth of the church.

Luke tells us that 3,000 were converted to the new faith. They had come from all over the known world, and after the festival, they returned to their homes, taking the new faith with them. In doing so, they spread the new faith across the empire. This is why there are Christians in Rome, Corinth, Antioch, and other places even before Paul got there.

Because of its significance and its connection to the birth of the church, Pentecost became a Christian celebration as well as Jewish. For Christians, it was no longer connected to the temple or to the Jewish pilgrimage festival. Instead, it is the day where we celebrate the gift of the Holy Spirit and God’s power within our world and our lives.

Later, when the Christian calendar was developed, the day of Pentecost was not only a day of celebration, but it also shaped two of the seasons. The season of Easter, also known as the great 50 days, where we celebrate Jesus’ resurrection and what it means for us, ends with the day of Pentecost. And the next season, known as the “Season After Pentecost,” begins the day after Pentecost.

Because Passover (and Pentecost, which is fifty days later) are both linked to the Jewish lunar calendar and we operate on the solar calendar, the exact day of Pentecost, as well as the two seasons it shapes, change each year. This means that it can occur as early as May 10 or as late as June 13.