Sunscreens are intended to remain at original potency for up to three years. Some sunscreens include an expiration date indicating the time after which they are no longer effective.
For ideal sun protection as well as consistency, strength and sterility, use sunblock prior to the date listed. Dispose of sunscreen that is past its expiration date. If you purchase sunscreen that doesn't have a date, write the date of purchase on the bottle. Also, discard sunscreen that is more than 3 years old, has been exposed to high temperatures or has noticeable changes in color or texture. Remember that if you use sunscreen liberally and often, a bottle shouldn't last from one year to the next.