The first “decade” had nine years, and they have been ten years long since. That is commonly accepted. Thus, the “seventies”, “eighties”, “nineties”, and “aughts”!
Canuck, you can simply start counting the decade from the “zero” year by thinking of 1-1 on said year as a fraction of the year leading up to the completion of …. one. Thus, the first day of the decade remains resolutely 1-1-2010, or zero and 1/365th of the decade.
The first “decade” had nine years, and they have been ten years long since. That is commonly accepted. Thus, the “seventies”, “eighties”, “nineties”, and “aughts”!
Canuck, you can simply start counting the decade from the “zero” year by thinking of 1-1 on said year as a fraction of the year leading up to the completion of …. one. Thus, the first day of the decade remains resolutely 1-1-2010, or zero and 1/365th of the decade.