Easter for Christians is not just one day, but rather a 50-day period. The season of Easter, or Eastertide, begins at sunset on the eve of Easter and ends on Pentecost, the day we celebrate the gift of the Holy Spirit and the birth of the Church (see Acts 2).
Easter is also more than just an extended celebration of the resurrection of Jesus. In the early church, Lent was a season for new converts to learn about the faith and prepare for baptism on Easter Sunday. The initial purpose of the 50-day Easter season was to continue the faith formation of new Christians.
Today, this extended season gives us time to rejoice and experience what it means when we say Christ is risen. It’s the season when we remember our baptisms and how through this sacrament we are, according to the liturgy, “incorporated into Christ’s mighty acts of salvation.” As “Easter people,” we also celebrate and ponder the birth of the Church and gifts of the Spirit (Pentecost), and how we are to live as faithful disciples of Christ.
From http://www.umc.org/what-we-believe/why-is-the-easter-season-fifty-days-long
