The first two weeks during which your tattoo is healing are the most crucial, but direct sunlight will always pose a danger to your tattoo.
UV light rays degrade tattoo ink over time. If you want your tattoo to last, cover your tattoo with high SPF sunscreen. An SPF of 30 or higher is recommended.
For more information on tattoo care, see the other FAQs on 'How To Take Care of Your New Tattoo.'