To Matthew Bailey (letter, 'Wrong date', South China Morning Post, June 7), your father is correct. You cannot start a new millennium until you have completed the previous one.
A millennium is a thousand years. Two millennia are two thousand years.
The third millennium cannot start until those 2,000 years have been completed. That happens at midnight on December 31, 2000.
Therefore the third millennium (and the 21st century) begins on January 1, 2001.
GEOFF ALVES Sha Tin