Evidence shows that using sunscreen every day helps slow down the skin’s aging process and 80% of skin aging is caused by the sun and extrinsic aging factors. According to studies, people who use broad-spectrum sunscreen on a daily basis, with an SPF 30 or higher, not only experience 24% less skin aging, but also reduce the risk of skin cancer by 40%, than those who use sunscreen only intermittently.

You should apply sunscreen daily, 15-20 minutes before going outside and enough to actually be effective. An interesting fact is that majority of people when they apply sunscreen do not apply enough of it and do not re-apply it often enough. The average person in a bathing suit needs a full ounce to completely cover all exposed areas, and every 2 hours. In fact, dermatologists actually recommend using sunscreen daily regardless of the season or weather or cloud coverage. Whether you will be inside or outside, you also come in contact with UV light through windows and UV light can also pass through clouds.

Some studies listed below:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3790843/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759112/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9025621/