How Do You Correctly Count the 20th Century? Explanation and Dates

Learn how to accurately count the 20th century, including its start and end dates, and understand century numbering rules.

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The 20th century began on January 1, 1901, and ended on December 31, 2000. In general, centuries are counted by taking the ordinal number and adding 1 to the starting year of the preceding century. For example, the 21st century started in 2001.

FAQs & Answers

  1. When did the 20th century officially begin and end? The 20th century began on January 1, 1901, and ended on December 31, 2000.
  2. Why does the 21st century start in 2001 instead of 2000? Centuries are counted starting from year 1, so the 21st century starts in 2001, following the completion of the 20th century on December 31, 2000.
  3. How are centuries counted in general? Centuries are counted by adding 1 to the starting year of the previous century’s first year, meaning the 1st century is years 1-100, the 2nd century is 101-200, etc.

Watch More

For more on historical timelines and century calculations, check out our related videos explaining the Gregorian calendar, millennium counting, and the history of the modern era.

  1. Why Is the Year 2000 Considered Part of the 20th Century, Not the 21st? Discover why the year 2000 marks the end of the 20th century and why the 21st century begins in 2001, based on how centuries are counted.
  2. Why Is the 21st Century Called That Instead of the 20th Century? Understand why the 21st century starts in 2001, not 2000, and how century numbering works historically.
  3. Why Does the 20th Century Start on January 1, 1901? Discover why the 20th century begins on January 1, 1901, and how centuries are calculated based on year counts.
  4. Why Is the Year 1900 Called the 20th Century? Explained Discover why the year 1900 is part of the 20th century and how centuries are counted from year 1 to 100, 101 to 200, and beyond.
  5. Why Does the 21st Century Start in the Year 2000? Learn why the 21st century begins in 2000 and how centuries are counted from year 1 to 100 in this clear explanation.
  6. Why Is the Year 2000 Considered Part of the 21st Century? Learn why the year 2000 is included in the 21st century and how the Gregorian calendar counts centuries without a year zero.
  7. Why Is the 2000s Called the 21st Century? Explained Learn why the 2000s are part of the 21st century and how centuries are numbered based on years covered.
  8. Why Is the Year 1800 Called Part of the 19th Century? Learn why the year 1800 falls in the 19th century and how century numbering works historically and mathematically.