1912 - nineteen twelve 1921 - nineteen twenty-one 2000 - two thousand / the year two thousand

"And how about 'in the 2000.' " You must mean "in the year two thousand." I use the nineteenth and twentieth centuries as an enumeration guide. "Twenty hundred" sounds bad. It would be incorrect to say that, even though "nineteen hundred" was the most preferred form for reporting 1900. We never hear "twenty hundred" said for identifying that year. Saying "eighteen hundred" was and is okay for reporting the year 1800, and "the eighteen hundreds" was the proper orally spoken form for referring to the general historical period or century of the 1800s. However, ten and twenty are major change or breaking points for pronunciation in the English numbering system. So, for the years 2010-2099, saying "Twenty ten" through "twenty ninety" is correct. I hesitate to add the "and" between the paired, double digit numbers. That is, unlike you I don't say "Twenty and ten" or "twenty and ninety-nine." I say "twenty ten" and "twenty sixteen" (for this year). But you are still historically correct in doing so. It's not wrong. I think any loquacious British would love it! (Notice that as I am American, I don't say "any loquacious British person." I shorten the phrase to "any loquacious British or Brit.")

"I heart someone said ' in the 1921' is 'ninteen hundred and twelve'. But I always said 'nineteen twelve'. Answer: I think you mean that you heard someone say '"in the year 1912," and that you always say "nineteen twelve" (and not "nineteen hundred and twenty-one"). Well, either one is correct when you say "in the year" before the four numerals. "In the year 1912" is a historical notation; it is more formal, thus longer. It is in the form of reporting a date for historical purposes. I've heard the British say "and" more often than I have heard Americans do it. It is more formal and more proper historically to say the longer, more complete version - "nineteen hundred and twelve." But American native speakers are famous for shortening phrases, and that includes the reporting of years and dates. Many Americans don't know this, having learned only one national variety of English. You start recounting the years from the beginning of a century, saying (in your example) "nineteen hundred." Then you should ad the British I.D. identifier "oh" (and not the counting "zero") instead of "hundred" and drop the "and" for the next nine years prefixed by the integer zero. That is, say "nineteen oh one" for 1901 through "nineteen oh nine" for 1909, and not "nineteen zero one" (for 1901), etc. Both British and Americans say "oh." We don't say "zero" or the integers 1-9 alone in nominal numbers, i.e., numbers of identification. For identifying the years 1910 through 1999, you split the date into pairs or couplets (as if it's 19/10), saying "nineteen (hundred) and ten," or "nineteen ten." We continue this practice through the year "nineteen (hundred) and ninety-nine"/"nineteen ninety-nine" (1999). In these double-digit ending dates (1910-1999), "and" is perfectly fine to say between the two pairs; especially when you formalize it by adding "the year" before it - like Michael said here.