Decade & Century Calculator
Decade & Century Calculator
Determine the exact Century, Decade, and Millennium of any given year.
The Decade
1940s
The Century
20th Century
The Millennium
2nd Millennium
Understanding Time Periods
In historical terms, a Decade is a period of 10 years, a Century is a period of 100 years, and a Millennium is a period of 1000 years. Because the calendar started at Year 1 (there was no Year 0), centuries are technically counted ahead of their numerical prefix (e.g., the 1900s are the 20th Century).
Frequently Asked Questions
Did the 21st Century start in 2000 or 2001?
Technically and mathematically, the 21st Century began on January 1, 2001, and will end on December 31, 2100. This is because the Gregorian calendar does not have a year zero.