Sunrise-Sunset is a free online tool that provides users information about day length, twilight, sunrise and sunset times for any location in the world. Their purpose is to make it easy for everybody to access Sun related information through simple tools that offer accurate information.
It's important to note that both sunrise and sunset are 'instants'. The time range during which the day becomes night or vice versa is called twilight. It is possible to distinguish between the morning twilight, that happens between dawn and sunrise and the evening twilight, that happens between sunset and dusk each day. Duration of twilight actually depends on a geographic location on Earth and date of the year.