visual basic mod function problems

Hey im kind of new to visual basic and pretty much all programing, but here is what I have to do. I have to make a calculator that will calculate the day of the week after the user enters the month, day of the month, and the year. I have everything good to go but i am having problems with the leap year test. I'm not completely sure how to use the mod function, and I cant find much info on it online; basically this is what i have for it but it does not seem to be working. Y is the variable for the year that the user selects.

If (Y Mod 400 = True and Y Mod 100 = True) Then
For feb2 = 1 To 29
Select Case ListBox1.SelectedItem
Case ("Febuary")
ListBox2.Items.Add(feb2)
Y = ListBox3.SelectedItem
End Select

Next
End If

Perhaps you should try joining a forum which specifically mentions "visual basic" somewhere in the title.

We deal with C, C++, C# here.

Completely the wrong place to ask. But Mod returns the modulus - i.e. the remainder after dividing by whatever. X Mod 400 will return the remainder after dividing by 400. So 801 Mod 400 is 1, for instance. Not True/False.