What Is the Length of a Century?

A century has 100 years in it. A century is theoretically any period of 100 years, but in practise, it is thought to begin with the year that ends in one and end with the year that ends in 00 or 100. For instance, the 20th century spanned from 1901 to 2000. Beginning in 2001, the 21st century will last until 2100. The Gregorian calendar, sometimes known as the New Style Calendar, provides the basis for this time measurement.


Ten decades, or groups of ten years, make up each century. Decades can encompass any 10-year period, just like centuries can. In contrast, a decade on the Gregorian calendar starts in the year that ends in one and ends in the year that ends in zero.

For instance, the 1990s began in 1991 and came to a conclusion in 2000. It’s more typical for people to begin and terminate one year early, though. The 1990s in this instance started in 1990 and ended in 1999.


Years are the building blocks of decades and millennia. A year is a 12-month period with January 1 as the start date and December 31 as the end date. Additionally, there are around 365.25 days in a year. However, the majority of people believe that a year only has 365 days.

Therefore, every four years, those four additional quarters combine to form a year of 366 days. It is referred to as a leap year. The time it takes for the Earth to complete one rotation of the sun is one year.


There are 12 months in a year. Some months have 31 days, including January, March, May, July, August, October, and December. The months of April, June, September, and November each have 30 days. Normally, February has 28 days, but in a leap year, it also has a 29th day. The moon’s orbit determined when the months began and ended.

Weeks and Days

Days are intervals of time that last approximately 24 hours and begin at midnight and end at 11:59 p.m. every day. The time it takes for the Earth to rotate on its axis is equal to one day.

The seven days of the week are Monday through Sunday. They are also known as the workweek. The weekend is defined as Saturday and Sunday, whereas the week is defined as Monday through Friday. In a year, there are 52 weeks.


Counting the four seasons—spring, summer, autumn, and winter—is another method of gauging time. The tilt of the Earth’s axis as it rotates around the sun is what causes the seasons to change. A season typically lasts three months. The spring equinox occurs in March, signalling the start of spring.

The summer solstice occurs in June, signalling the start of summer. The autumnal equinox occurs in September, signalling the start of autumn. The winter solstice, which occurs in December, marks the start of winter.

Calendar used by Gregorian

The Gregorian calendar, which was formally adopted by Pope Gregory XIII in 1582, serves as the foundation for the majority of time measurements used today. The Julian calendar, which was discovered to be marginally wrong, was replaced by it. It was first used in Italy, Poland, Portugal, and Spain.

Many Protestant nations were hesitant to utilise it because they believed it was a Catholic plot to stifle their opinions. It was adopted in 1752 by England and the colonies that would later become the United States. It continues to be the most popular calendar.

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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