If you are in the path of totality the eclipse begins with a partial phase in which the Moon gradually covers more and more of the Sun. This typically lasts for about an hour until the Moon completely covers the Sun and the total eclipse begins. The duration of totality can be as short as a fraction of a second, or as long as about 7.5 minutes. The longest total eclipse in the 21st century is 6 minutes, 39 seconds. You will have to wait until the year 2150 to experience a total eclipse of more than 7 minutes.