Easter event is only active until the 25th of April. If you wish to enable it outside its season, go to the settings and set Easter Event from ON/OFF to ALWAYS :).
The event basically adds an NPC with a special trade and Easter eggs to find. These eggs have a random small chance to appear in any situation where you use the explore button. Find the NPC when the day progress bar is green and she will inform you how the trade works :).
