These diverse factors make it tough to recommend the correct amount of sunlight for vitamin D to a person. To prove this the Vitamin D council gives a few examples-
“At noon during summer in Miami, someone with a medium skin tone would need to expose one-quarter of their skin to sunlight for 6 minutes.”
“At noon during summer in Boston, someone with a darker skin tone would need to expose one-quarter of their skin to sunlight for 2 hours.”