The importance of Easter is not the certain day but, it is pointing to the cross, the place where Jesus purchased us with his blood. "Without the shedding of blood the is no remission (forgiveness) of sin" He made a way for you and I to receive eternal life. Read Romans 10:9-13. Hope this answers your question.
Christ has risen from the dead.
The importance of Easter is that after three days of his death Christ had rised and became alive again! So just to give honour respect etc to this Easter Is celebrated in the happiness n joy of Christ rising from the dead!