Calculate Age (Years + Months + Days) in C#

Age.cs

/**
* Calculate Age in C#
* https://gist.github.com/faisalman
*
* Copyright 2012-2013, Faisalman <[email protected]>
* Licensed under The MIT License
* http://www.opensource.org/licenses/mit-license
*/

using System;

public class Age
{
  public int Years;
  public int Months;
  public int Days;
  
  public Age(DateTime Bday)
  {
    this.Count(Bday);
  }
  
  public Age(DateTime Bday, DateTime Cday)
  {
    this.Count(Bday, Cday);
  }
  
  public Age Count(DateTime Bday)
  {
    return this.Count(Bday, DateTime.Today);
  }
  
  public Age Count(DateTime Bday, DateTime Cday)
  {
    if ((Cday.Year - Bday.Year) > 0 || 
        (((Cday.Year - Bday.Year) == 0) && ((Bday.Month < Cday.Month) || 
          ((Bday.Month == Cday.Month) && (Bday.Day <= Cday.Day)))))
    {
      int DaysInBdayMonth = DateTime.DaysInMonth(Bday.Year, Bday.Month);
      int DaysRemain = Cday.Day + (DaysInBdayMonth - Bday.Day);
  
      if (Cday.Month > Bday.Month)
      {
        this.Years = Cday.Year - Bday.Year;
        this.Months = Cday.Month - (Bday.Month + 1) + Math.Abs(DaysRemain / DaysInBdayMonth);
        this.Days = (DaysRemain % DaysInBdayMonth + DaysInBdayMonth) % DaysInBdayMonth;
      }
      else if (Cday.Month == Bday.Month)
      {
        if (Cday.Day >= Bday.Day)
        {
          this.Years = Cday.Year - Bday.Year;
          this.Months = 0;
          this.Days = Cday.Day - Bday.Day;
        }
        else
        {
          this.Years = (Cday.Year - 1) - Bday.Year;
          this.Months = 11;
          this.Days = DateTime.DaysInMonth(Bday.Year, Bday.Month) - (Bday.Day - Cday.Day);
        }
      }
      else
      {
        this.Years = (Cday.Year - 1) - Bday.Year;
        this.Months = Cday.Month + (11 - Bday.Month) + Math.Abs(DaysRemain / DaysInBdayMonth);
        this.Days = (DaysRemain % DaysInBdayMonth + DaysInBdayMonth) % DaysInBdayMonth;
      }
    }
    else
    {
      throw new ArgumentException("Birthday date must be earlier than current date");
    }
    return this;
  }
}

/**
 * Usage example:
 * ==============
 * DateTime bday = new DateTime(1987, 11, 27);
 * DateTime cday = DateTime.Today;
 * Age age = new Age(bday, cday);
 * Console.WriteLine("It's been {0} years, {1} months, and {2} days since your birthday", age.Year, age.Month, age.Day);
 */

Im learning can anyone please explain the code ?

I use this code to calculate Age and it is very simple:
`DateTime birthdays = DateTime.Parse(dateTimePicker1.Text);
DateTime dateNow = DateTime.Parse(dateTimePicker2.Text);
TimeSpan urBirthday = dateNow - birthdays;
label3.Text = urBirthday.Days.ToString();
label3.Text += "\n All Day :" + string.Format("{0} total days ",urBirthday.TotalDays);
int nowMonth = dateNow.Month;
int birthMonth = birthdays.Month;
int nowYears = dateNow.Year;
int birYear = birthdays.Year;

            int nowDays = dateNow.Day;
            int biDays = birthdays.Day;
            int yy = nowYears - birYear;
            int mm = nowMonth - birthMonth;
            int dd = nowDays - biDays;
            if (mm < 0)
            {
                yy--;
                mm = mm + 12;
            }
            if (dd < 0)
            {
                mm--;
                dd = dd + 31;
            }

            label3.Text += "\n\n year :" + string.Format("{0} years",yy);
            label3.Text += "\n month :" + string.Format("{0} months",mm);
            label3.Text += "\n days :" + string.Format("{0} days",dd);`