How long does it take to heal from sun burn that did not blister?

SImple Burn Care. Sunburn is response of the tissues to injury from solar radiation. It is simply inflammation which means increase blood flow to the area to promote healing. Do not use ice as this can injure already injured skin. Cool water soaks can help as can taking anti-inflammation medicines like Motrin or advil (ibuprofen). Avoid any further damage as this can cause scarring . Good skin cream applied daily/gently helps.
Avoid the sun. You must stop the burning in order to heal. A sunscreen will help protect you from further sun, but it is not very good protection. The key to heal is sun avoidance, not sunscreen. You will need to moisturize your burn and keep it out of the sun. In the future, use an spf of no more than 50 and one that contains a metal such as zinc or titatnium oxide and wear a wide-brimmed hat.