Daylight Saving Time, often abbreviated as DST, is the practice of setting clocks forward by one hour from standard time during the summer months and back again in the fall to make better use of natural daylight.
Daylight Saving Time is when we change the clocks to make evenings longer in the summer. You probably know it as 'spring forward, fall back.' In the spring, we move the clock forward one hour, and in the fall, we move it back one hour to return to standard time. The main idea is to save energy and enjoy more daylight after work.
Daylight Saving Time (DST) is the practice of setting clocks forward one hour from standard time during the summer months to make better use of natural daylight. The common mnemonic "spring forward, fall back" describes the change.
For a complete history and discussion of its effects, read our full article: What is Daylight Saving Time (DST)? A Complete Guide.
UTC is the primary time standard by which the world regulates clocks. It's the successor to GMT and is based on atomic time for precision.
GMT stands for Greenwich Mean Time, the historic time standard based on the Prime Meridian in Greenwich, London.
The USA and its territories use 9 standard time zones. The 4 contiguous US states time zones are Pacific, Mountain, Central, and Eastern.
A leap second is a one-second adjustment added to UTC to keep it in sync with the Earth's irregular rotation.
