Sometimes when you move a rug or piece of furniture in a room with hardwood flooring, you notice that the previously covered area is a lighter shade than the wood that has been exposed. You might think the exposed wood should be lighter from fading, but actually hardwood flooring darkens over time.
Darkening of hardwood flooring begins after a few weeks of direct sunlight. Away from sunlight, it takes six to eight months. Direct and indirect ultraviolet rays from the sun darken the wood. Some wood, such as cherry, reaches its darkest color two or three years after installation. Other hardwood flooring darkens more each year it ages.
Wood that has just been cut looks much lighter than it looks after installation. Hardwood flooring samples are not newly sawn and will look a lot darker than the flooring you order according to the samples. It will eventually become the color you ordered, so you should consider this when choosing a sample. Wood such as Brazilian walnut has a large range of color when freshly cut, but over time it will turn medium to dark brown.
Areas of hardwood flooring covered by rugs or furniture won't darken as quickly as those exposed to direct and indirect ultraviolet rays. To avoid spotty floors, move rugs and furniture around often to let sun exposure affect all areas. Invest in room-darkening blinds that keep direct sunlight off floors. You can also cover large areas of your hardwood flooring with area rugs. This won't prevent darkening, but the wood won't darken as quickly.
You can always sand down and restain your hardwood flooring after it darkens. Or, install a wood a few shades lighter that what you want so you'll end up with the color you do want for a greater length of time.
Look closely at the warranty for your hardwood flooring. Color changes are cause by natural characteristics of the wood, not by mistakes in manufacturing and delivery. Most manufacturer's warranties won't cover darkening of wood flooring for this reason.