Why do we read some calendar years by their two-digit place value and not according on their numerical place value like: 1500s as fifteen hundreds and not one thousand five hundreds, 1895 as eighteen ninety five, 1903 as nineteen zero three or nineteen o-three? But we all know there is an exemption in the 21st century in which they are read: 2001 as two thousand one or twenty o-one, 2007 as two thousand seven or twenty o-seven, 2015 as two thousand fifteen or twenty fifteen. Is it because it's pleasing to hear or is there any reason behind this?