Eva cancellation policy is different for flights to/from the United States and all other flights.
For flights to/from the United States, you can cancel your ticket without a cancellation fee if you cancel within 24 hours of booking and submit a refund application within 24 hours of purchase. The ticket must have been purchased at least one week (168 hours) before the flight's departure date. The refund will include the full ticket price, minus any applicable taxes or fees.