using System;

public class Program

{

    public static void Main()

    {

        var l = new Learner{

            DateOfBirth = new DateTime(2018, 5, 30)

        };

        Console.WriteLine(l.IsLessThanThree);

        Console.WriteLine(l.IsLessThanFive);

    }

}

​

public class Learner {

    public DateTime DateOfBirth { get;set;}

    public bool IsLessThanThree => DateTime.UtcNow - DateOfBirth <= TimeSpan.FromDays(365*3);

    public bool IsLessThanFive => DateTime.UtcNow - DateOfBirth <= TimeSpan.FromDays(365*5);

}