Spring and Hope
Bunnymund represents spring and hope, those two things go together hand in hand.
Spring is one of the four seasons (and one of the two that is vanishing). Spring aside of being a season actually means also rebirth, renewal, rejuvenations, resurrection ect because it's the moment when Nature comes back to life and there is new life in both flora and fauna. In Northen hemisphere Spring begins with the March equinox that normally falls on 21st March and becomes also the first day of spring, and ends on 21st June which is solstice.
Hope is what makes us go forward, it's the one that dies the last. Hope is something that we cultivate and never lose it. It's a way of being, when there are difficult time, is hope that makes you go on. Do not think it's the same as optimism.
Hope is the state which promotes the desire of positive outcomes related to events and circumstances in one's life or in the world at large