Sunday before Easter is Palm Sunday. The feast exists both in Western and Eastern Christianity, but falls on different dates.
Youth Day is celebrated in many countries around the world on different dates, however, there is also a global event, known as World Youth Day. This observance was established by Pope John Paul II in 1985 and it's annually celebrated on Palm Sunday.
Palm Sunday is a Christian moveable feast that commemorates Jesus' triumphal entry into Jerusalem that is described in the four canonical Gospels. It is celebrated on the Sunday before Easter.