The general perception of a tan is coloration of the skin after sun exposure that increases with duration and intensity of sun exposure. However, there is more to it... Tanning can be Immediate or Delayed or Sunless/UV-less. Immediate tanning, also known as Immediate Pigment Darkening, is the immediate discolouration of the skin lasting for a few hours to few days then fading away Delayed tanning develops 72 hours after UV exposure and lasts for several weeks Sunless or UV-le