What is the difference between a day cream with UV protection and a sunscreen?
The requirements for labeling UV protection are the same for sunscreen and day cream with sun protection. That is is a product marked with SPF30, it must have passed the same tests, and satisfy the same requirements for UV protection, regardless of whether it is a sunscreen or a day cream with sun protection.
Remember that all products with UV protection (both sunscreens and day creams with sun protection) must be applied in sufficient quantity and frequently enough to have the specified UV protection. Water and sweat reduce the sun protective effect. If you are going to the beach or working out in the sun, you should therefore use a sunscreen that is waterproof instead of a non-waterproof day cream with sun protection factor.