readme.md

Shows how to get a person's age in years.

Below are two dates, current today's date, birthDate date of a person's birth.

int current = 20240403;
int birthDate = 19000924;

Format for both yyyyMMdd

Subtract current from birthDate, remove the last four characters to get years old.

int yearsOld = int.Parse((current - birthDate).ToString()[..^4]);

Variations

1️⃣

Console.WriteLine(
    (current - birthDate).ToString()
    .RemoveLastCharacters()
    .Age());

2️⃣

int now = int.Parse(DateTime.Now.ToString("yyyyMMdd"));
int dob = int.Parse(new DateOnly(1900,9,24).ToString("yyyyMMdd"));
int age = (now - dob) / 10000;
Console.WriteLine(age);

3️⃣

Console.WriteLine(new DateOnly(1900, 9, 24).GetAge());

Program.cs

static void Main(string[] args)
{

    int current = 20240403;
    int birthDate = 19000924;

    Console.WriteLine((current - birthDate).ToString()[..^4]);

    Console.WriteLine((current - birthDate).ToString().RemoveLastCharacters());


    int now = int.Parse(DateTime.Now.ToString("yyyyMMdd"));
    int dob = int.Parse(new DateOnly(1900,9,24).ToString("yyyyMMdd"));
    int age = (now - dob) / 10000;
    Console.WriteLine(age);

    Console.WriteLine(new DateOnly(1900, 9, 24).GetAge());

}

SomeExtensions.cs

public static class SomeExtensions
{
    public static int GetAge(this DateOnly dateOfBirth)
    {
        var today = DateTime.Today;

        var value1 = (today.Year * 100 + today.Month) * 100 + today.Day;
        var value2 = (dateOfBirth.Year * 100 + dateOfBirth.Month) * 100 + dateOfBirth.Day;

        return (value1 - value2) / 10000;
    }


    public static string RemoveLastCharacters(this string sender, int count = 4) 
        => sender[..^count];

    public static int Age(this string sender) => int.Parse(sender);

}