Tomorrow (25/3) is Palm Sunday, that is when Easter (so far as I am aware, and concerned) starts. Jesus riding into Jerusalem on a donkey with crowds waving palm leaves and cheering him. Then there is the whole drama of Easter week - last supper, betrayal, imprisonment, Pontius Pilate freeing Barabbas etc. all leading to Good Friday when Jesus was crucified. Easter Sunday follows when he rose again, the stone was found rolled away from the tomb etc..
Easter Monday is - quite frankly I'm not too sure, I'd have to look it up, but a day of assimilation and celebration possibly. Best I can do off the cuff without going into a lot of detail.