var zoneEntityID = null;

var dayNightDuration = 120; // in seconds

var entities = Entities.findEntities({ x: 0, y: 0, z: 0 }, 600000);
for (var i in entities) {
    var entityID = entities[i];
    var name = Entities.getEntityProperties(entityID, 'name').name;
    if (name == 'Day/Night Cycle') {
        zoneEntityID = entityID;
        break;
    }
}

if (zoneEntityID) {
    print("Found Day/Night zone entity: ", zoneEntityID);
    Script.setInterval(function() {
        var seconds = (Date.now() / 1000) % dayNightDuration;
        var angle = seconds / dayNightDuration * (Math.PI * 2);
        Entities.editEntity(entityID, {
            keyLight: {
                direction: {
                    x: -Math.cos(angle),
                    y: -Math.sin(angle),
                    z: 0
                }
            }
        });
    }, 100);
} else {
    print("Could not find Day/Night zone entity");
}