Greenwich Mean Time (GMT) is a time system originally referring to mean solar time at the Royal Observatory in Greenwich, London. For example, GMT-4 means that Standard Time is 4 hours behind of Greenwich Mean Time. New York City uses GMT-4 as its Time Zone. Learn more on Wikipedia.

Golden Hour

The time of day when the sun is low in the sky, producing a soft, diffused light which is much more flattering than the harsh midday sun. This type of light produces less contrast, reducing the chances of losing parts of your subject in strong shadows or blown-out highlights. The warm glow adds a pleasing feel to the scene, and the long shadows help to pick out details, adding texture and depth to the image. PhotoPills considers the golden hour as the time, both morning and evening, when the center of the sun is between 6 degrees above the horizon and 4 degrees below the horizon (6º,-4º).  Learn more on Wikipedia.