How effective is it? What SPF is best? Is it safe to wear every day? Credit...By Maggie Shannon While most experts agree that you should use sunscreen year-round to prevent damage from the sun, harmful ultraviolet rays are strongest during late spring and early summer. We’ve partnered with health reporters from Wirecutter, The New York Times site that reviews and recommends products (and publishes annual ratings of sunscreens for the face and body), to answer some of the most common questions readers have about sunscreen, including how safe and effective it is, how to use it properly, and how to pick the right one for you.