Many people think sunscreens are only needed when going out in the sun, this is false. Incidental exposure adds up. Going to and from your car, sitting by a window at lunch, and even office lighting all add up over time. This is why wearing sunscreen everyday, all year long, will give you optimal protection. A minimum SPF of 30 or higher EVERYDAY, reapplying when needed (i.e., sweating, long sun exposure, swimming, etc.) is the best remedy to prevent extensive sun damage.