这个让人想到 Y2K 问题
the mid-1910s = around 1905;
the mid-1900s = around 1950;
the mid-2000s = around 2005 或 around 2050 或 around 2500
(以上数字后都是 +/- 的)
表示2000- 2004之类,
in the early years of the twenty-first century
at the beginning of the twenty-first century
around the middle of the first decade of the twenty-first century