Once a day means what it says you apply the lotion once preferably after a shower 15 minutes before you expose yourself to direct sunlight and the protection lasts all day all the range has been dermatologically tested to ensure that no problems occur with regular use and to show that it meets the uva and uvb requirements having a 4 star uv protection of superior you know once a day is high quality once a day protection spf 40 gives the family the freedom to enjoy the day in the k