Throughout my life, I’ve always heard people refer to the early 21st century years as “two thousand and X”. For example, they pronounced 2001 as “two thousand and one”. In my experience, during the mid-2010s there seemed to be a shift in the way people said it, and the first time I heard someone say it differently was in 2016, where they pronounced it as “twenty sixteen”.

Most people I’ve heard pronounced the late-2010s years as “two thousand and X”, although the pronunciation “twenty X” had started to catch on fast. By the year 2020, almost nobody used the “two thousand and X” pronunciation, except for very old people I knew. For example, most people would pronounce 2024 as “twenty twenty-four” and not “two thousand and twenty-four”.

My question is: what year is the cutoff date for pronouncing the early 21st century years as “two thousand and X?” I’ve always heard people say it that way prior to 2016, I’ve never heard someone pronounce, say, 2007 as “twenty oh seven”.

I hope I was able to properly articulate what I’m trying to say.