[dead]
ISO 8601 would like a word with you:
Actually you are right. It does make sense, I just always interpreted decade as a different abstraction.
2019 could be the end of "my decade" only if there was a year zero, which does not exist in gregorian calendar. The second millenium ended in year 2000, so the 202 decade ends in 2020.
The twenties are a decade.