equation of time

noun phrase

Definition of equation of time

: the difference between apparent time and mean time usually expressed as a correction which is to be added to apparent time to give local mean time The Equation of Time is the difference between your local apparent solar time, when the Sun crosses your meridian, and local mean solar time, which is the average rate of solar time used in clocks. Because the Earth travels at varying speeds as it traverses its elliptical orbit, the difference can be as much as 16 minutes.— Kathleen Hill Zeller

First Known Use of equation of time

1645, in the meaning defined above

Keep scrolling for more

Learn More about equation of time

Time Traveler for equation of time

Time Traveler

The first known use of equation of time was in 1645

See more words from the same year

Statistics for equation of time

Cite this Entry

“Equation of time.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/equation%20of%20time. Accessed 28 Jan. 2021.

Comments on equation of time

What made you want to look up equation of time? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

Test Your Vocabulary

Slippery Words Quiz—Changing with the Times

  • ducreux self portrait yawning
  • What is an earlier meaning of nice?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Universal Daily Crossword

A daily challenge for crossword fanatics.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!