Several online calculators allow users to enter their local city, state or ZIP code and receive accurate sunset times, including timeanddate.com and calendarupdates.com. In addition, most weather applications for smartphones, like The Weather Channel and Apple's Weather app include daily local sunrise and sunset times.
Also, local television news weather reports usually include sunrise and sunset times for the current day or the following day. Weather reports in local newspapers also traditionally include sunrise and sunset times for the current day.
Those who wish to know the times several days in advance may wish to visit SunriseSunset.com, where users can enter their local city and print a monthly calendar showing sunrise and sunset times. This is also a helpful tool for teaching children how the times fluctuate throughout the year.
Sunset and sunrise times are actually calculated mathematically using something called the sunrise equation, which takes into account the longitude of the location, the angle of the sun relative to that specific location, and the date. This equation holds true everywhere on Earth between the Arctic circle in the north and the Antarctic Circle in the south. Above the Arctic Circle and below the Antarctic circle, there is at least one day a year with no sunrise or sunset.
Rutger's Physics website offers a detailed mathematical explanation.