China driving license can be used in Denmark for 14 days.
Remember to keep your headlights on at all times, it's a must in Denmark even during the daytime. Newer cars in Denmark are even programmed in a way that you can't turn off the lights in the first place.
Also, seat belts are a national legal requirement and must be worn at all times.
Lastly, make sure to carry a warning triangle in the trunk your car, which is generally standard equipment in rental cars.
