Easter is an important Christian feast
At Easter the Christians celebrate that Jesus has stood up from the dead (on the third day after his crucifixion). It is celebrated on Sunday and Monday (hence the terms Easter Monday and Easter Sunday are also used. 40 days after Easter it is Ascension Day. Easter is celebrated on the first Sunday after the first full moon in spring (at the earliest 22 March). Friday before Easter is Good Friday, on that day the suffering of Jesus Christ is commemorated.
The Easter bunny has nothing to do with this biblical disorder. Rabbits and hares have long been a symbol of fertility. The fertile hare is a sign of spring when new life is created in nature.