Standard time is determined by checking clocks against a sundial. When the Sun is directly overhead and shadows are at their shortest, it is said to be noon. As already discussed, many areas do not observe true Sun time due to political and social borders.

During the First World War, Germany instituted a daylight saving program to save power. They ordered everyone to set their clocks ahead by one hour, or one hour ahead of standard Sun time. Doing this made it so that it was light longer into the evening, saving their country energy in the form of electricity.

In 1918 the United States began a similar policy. Today, most countries around the world observe Daylight Saving Time. Daylight Saving Time usually begins in April and ends in October in the Northern Hemisphere, after which clocks are set back to standard Sun time.