There has been much debate about when the old decade ends and the new one begins. Some say the old decade ended on December 31, 2019, and the start of the new one began January 1, 2020. For others, the new decade doesn't start until January 1, 2021; the old one concluding on December 31, 2020.

Do decades end in 9 or 0?

Decades—periods of ten years—begin when the year count ticks over from a year ending with 9 to a year ending with 0. For example, New Year's Day 1980 marked the beginning of the eighties.

How long is 20 years called?

' So, 20 years = 2 Decades. 30 years = 3 Decades. 40 years = 4 Decades.