Those who were born on November 30, 1999 (and even moreso the parents of such a person) have probably realized that their exact age—to the day—is the same as the daily date. Today, August 3, 2015, they are 15 years, 8 months, and 3 days old. The only time they might employ a little carry-over math is during their actual birthday (when they know their age) and the month of December, when 12 months old could be translated as 1 year and added to the year column.
Their age is tracked, for their convenience or for their torment. A cliche would be that it is what they make out of it, but what has it made out of them? Born into an arbitrarity that marks them from birth onwards, so arbitrary is the changing of a day on Earth that a new day arrives more than 20 different instances. Their were many millenium babies, and probably several pregnant families who dreamed or pursued putting a 40 week pregnant woman on a plane to a timezone that would reward them with the first born of the millennium. There are twins (or triplets and beyond) who have to wander at being born in different millenniums.
I am categorizing this as unfinishe (a play on words) for the moment because there are many more political lessons to tease out. The societal (mis)use of temporal tracking and the repercussions, societal and not, of such activities is sure to cover a large spread.