converting date to age?

If you have a date, for example 06/12/78
How can you get the age of a person who is born on that date?

Here's what I use to calculate the age in C#

Code:

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private int CalculateAge(string date)
{
  DateTime d1 = Convert.ToDateTime(date);
  int age;
                       
  if(DateTime.Now.Month < d1.Month || DateTime.Now.Month == d1.Month && DateTime.Now.Month < d1.Day)
        age = DateTime.Now.Year - d1.Year - 1;
  else
        age = DateTime.Now.Year - d1.Year;

  return age;
}

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