We all need to place sunscreen on everyday! Yes everyday 30 minutes prior to going out. What is SPF? Sun protection factor. Multiple the SPF number by 10 and it gives you the minutes of protection you get from UVA & UVB rays. Example 15 SPF x10 is 150 minutes of protection minus the 30 minutes the product needs to be on your skin to be effective. Key point, harmful UVA rays penetrate clouds, windows, water, and increase their damaging capabilities in higher altitudes.