See these articles:
http://www.codeproject.com/KB/datetime/[
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There is more than enough information for you to learn everything about that topic.
For example to get the age:
DateTime bday = new DateTime(1980, 11, 8);
DateTime now = DateTime.Today;
int age = now.Year - bday.Year;
if (bday > now.AddYears(-age)) age--;
MessageBox.Show("Age is: " + age.ToString());
To get today:
MessageBox.Show("Today is: " + DateTime.Now.ToShortDateString());
MessageBox.Show("Today is: " + DateTime.Now.ToShortDateString());
MessageBox.Show("Todays day is: " + DateTime.Now.Day.ToString());
MessageBox.Show("Todays month is: " + DateTime.Now.Month.ToString());
MessageBox.Show("Todays year is: " + DateTime.Now.Year.ToString());
MessageBox.Show("Todays weekday is: " + DateTime.Now.DayOfWeek.ToString());