years

The year is usually read two numbers at a time

• 1950 "nineteen fifty"
• 1983 "nineteen eighty-three"
  
  But
  
• 1809 "eighteen oh nine"
• 1900 "nineteen hundred"
• 2001 "two thousand and one"

The first two numbers of the year are sometimes omitted:

Where were you in '92

BC = "before Christ"
AD = Anno Domini "in the year of our Lord"

The Roman poet Ovid :43BC -18AD