When Does the Next Decade Begin: 2020 or 2021?

The debate over when the next decade begins is a common topic of discussion, particularly around significant years like 2020. According to widely accepted conventions, the next decade starts in 2021, marking it as the beginning of the 2020s.

The Definition of a Decade

A decade is a period of ten years. Given that the current decade is from 2020 to 2029, the next decade will span from 2021 to 2030. This follows the conventional understanding that a new decade commences with a year ending in '1'.

The Historical Background

The Gregorian calendar, the standard calendar in use today, was introduced in October 1582 and is a modification of the Julian calendar, which started in the Holy Roman Church in January 1544. The origin of the Julian calendar dates back to Julius Caesar.

It's important to note that no calendar system has a year zero, which means the decade and century start with a year ending in 1. Therefore, the 2020s began with 2021, not 2020.

Why 2021, Not 2020?

The Gregorian calendar does not use year zero, which means the first year of any new cycle (decade, century, millennium) is always a year ending in 1. For example, the 1700s (1701 to 1800) started with 1701, not 1700. This pattern holds true for the 2020s, which started in 2021, not 2020.

Conventions in Time Keeping

This convention is based on the lack of a year zero. If we were to count with a year zero, the start of each new decade, century, or millennium would be straightforward. However, without it, we follow a convention based on a year ending in 1. This is why 2030 marks the end of the 2020s and the beginning of the 2030s.

The Significance of Year 1

For calendrical purposes, the year 1 (often referred to as the start of the Common Era, CE) came into use after the introduction of the Gregorian calendar. The transition from the Before Christ (BC) era to the CE era is significant but not seminal, as it occurred well after the AD (Anno Domini) system was in place.

Thus, the new decade, century, or millennium always starts with a year ending in 1, while it ends with a year ending in 0. This is a longstanding convention that has been followed for centuries.

Conclusion

In conclusion, the next decade begins in 2021, not 2020. This is due to the absence of a year zero in the Gregorian calendar and the long-standing convention that each cycle (decade, century) starts with a year ending in 1. Understanding this convention is key to correctly marking and understanding time in our modern calendar system.