[{"eventDate":{"day":"01","month":"02"},"slug":"slug1"},{"eventDate":{"day":"21","month":"04"},"slug":"slug2"},{"eventDate":{"day":"02","month":"02"},"slug":"slug3"}]

db.collection.find({"$or":[{"eventDate.day":"01","eventDate.month":"02"},{"eventDate.day":"02","eventDate.month":"02"}]},{"slug":1})