When and why can you see your longest shadow?

The time of day in which your shadow is longest is right before sunset, but early enough that there is still a good amount of sunlight. Your shadow is at it's shortest at 12 noon. As the sun goes further down, you are blocking more and more of its rays. The same could be said in the morning as the sun is rising. You will cast a long shadow that grows shorter until the sun is directly overhead.