I am trying to write a program to determine if a year is a leap year or not. It is driving me nuts, i know nothing about leap years. Here is the question.

"The current calendar, called the gregorian calendar, was introduced in 1582. Every year divisible by four was declared to be a leap year, with the exception of the years ending in 00(that is, those divisible by 100) and not divisible by 400."

i cant figure out how to even go about it, here is as far as i got with my coding.
Code:
Public Class Form1

    Private Sub btnCalc_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalc.Click
        Dim year, value, value2 As Double
        year = CDbl(txtYear.Text)
        value = year / 100
        value2 = value / 4

        MessageBox.Show(CStr(value2))
        

    End Sub
End Class