Don't get us wrong — the sun is incredible. On a rational level, we know we can't live without it. On an emotional level, it makes us feel great. It's warm; it gives us energy. But too much time in the sun is never a good thing for your skin. A recent Olay study confirmed that it's the number one cause of premature skin aging. The number one cause. "Sun exposure disrupts your skin's barrier function; damages collagen, elastin, and DNA; and also interferes with the skin's ability to maintain hydration," says Joshua Zeichner, MD , an assistant professor in the dermatology department at Mount Sinai Medical Center in New York City. Not to mention the emission of free radicals in your skin caused by the exposure to UV radiation, which can lead to a variety of skin issues (dark spots, pigmentation).The best way to protect yourself from the sun is with sunscreen, right? Well, it's certainly the easiest way. Especially when you can work it right into your beauty routine with moisturizers spiked with broad-spectrum SPF, like the Olay Regenerist Micro-Sculpting Cream with SPF 30. "You have to get in the habit of using sunscreen every day, and using it in your moisturizer is 100% okay," says Dr. Zeichner. Just be sure you're applying enough and that you're wearing it regularly. And even then, SPF should only be one piece of your sun-protection regimen.After all, whenever you can see the sun, it can see you. So together with Olay and Dr. Zeichner, we tracked down some of the sneakiest ways the sun is damaging your skin. From boozy brunches to the altitude of your favorite vacay spot, there are many factors at play that can lead to skin damage. Arm yourself with the facts below, and you'll still be able to have fun in the sun — you'll just know the smart way to do it.