Wearing sunscreen is non-negotiable any time of year. But during the summer months, it becomes even more important because most of us spend even more time outside. Something you may not know? Many sunscreen brands say their products are best used within 12 months of opening. To tell if this is the case with SPF you own, look for a little symbol on the back of the bottle that says 12M. All of this is to say, if the last time you bought sunscreen was last summer, you may be due for a restock.