Today is the day we all turn our clocks back one hour, it's Daylight Saving Time.
Every year at the end of October or early November, clocks around the world will "fall back" giving us all one extra hour of sleep that night, and one less hour of sunlight in the evening for the rest of the season.
Daylight Saving Time is a time cycle that starts in the early spring when we "spring" forward and set our clocks ahead one hour.
Because the sun rises so early in the spring and summer months, setting our clocks ahead by an hour gives you more daylight in the evening.
In the fall, the exact opposite happens - we set our clocks back an hour (to Standard Time) to gain an extra hour of sunlight in the morning, so we're not heading off to school or work in the dark!
It wasn't until World War I that countries started to think of observing Daylight Saving Time.
The practice of switching the time around has been a muddle ever since.
In the United States, the government let individual states and cities decide whether or not they wanted to observe Daylight SavingsTime because it had angered so many people originally.
At the time, many Americans were farmers, used to getting up early and going to bed early.
It wasn't until the mid-1970s that an official law on the matter was passed.
And still there are states, such as Hawaii, most of Indiana and Arizona, who do not observe Daylight Saving Time.