All wood flooring is more or less photosensitive, and some species are very sensitive to ultra-violet light. It’s important to prevent the sun’s rays from discoloring your floor by shielding it against direct sunlight. However, it’s normal for hardwood floors exposed to even indirect sunlight to darken or lighten after a while, so for consistency, rotate rugs and furniture to equal out the amount of sunlight exposure and variances will eventually fade away.