Try this sample and adapt it to your form:
using System;
public class Program
{
public static void Main()
{
DateTime dob = new DateTime(1995, 2, 10);
DateTime today = DateTime.Today;
int age = today.Year - dob.Year;
if (dob.AddYears(age) > today)
{
age--;
}
Console.WriteLine(age);
}
}
Refer:
DateTimePicker.Value Property[
^]