If condition not met using Or keyword - vb.net

Question

This is my first time asking in Stack Overflow :)
I have a program that lets the user pick a date in a combobox and display it on the label. The other parts of the code for that is fine but I cant make exception for months with special days (like february which only has 29 days in leap years).
I tried using the If/Else statement so that when the users click the years 2016,2012,2008 and 2004 and february it will display on the combobox named "day" 1 to 29 and if the users click february but not the specified dates it will display 1 to 28:
If month.SelectedItem = "Feb" And year.SelectedItem = "2016" Or "2012" Or "2008" Or "2004" Then
Dim jkl As Integer
For jkl = 1 To 29
day.Items.Add(jkl)
Next
ElseIf month.SelectedItem = "Feb" Then
Dim poi As Integer
For poi = 1 To 28
day.Items.Add("poi")
Next
End If
But unfortunately when i debug it, when i select dates other than the specified in the first If statement the combo box named day only displays 29 instead of 28. I tried changing the order of the conditions, changing the separator of the numbers to "&" but it is still the same.
I hope someone gets to the bottom of this. I feel like its in my structure that is wrong but even if I change the order everytime and it is still displaying the same bug.
I tried searching here but I cant find one like my condition even remotely similar.

Answer 1

Turn Option Strict On, it will help you detect these errors right away. VB does not handle If statement like this, what you wrote doesn't do what you think it does. You need to specify both side every time.
If month.SelectedItem = "Feb" And (year.SelectedItem = "2016" Or year.SelectedItem = "2012" Or year.SelectedItem = "2008" Or year.SelectedItem = "2004") Then
As for your logic, there are formula to detect leap day. It might be better to use it instead.
Lastly, near the end, you add the string and not the variable value.
day.Items.Add(poi)

Answer 2

I think you should use here the DateTime functions:
DateTime.DaysInMonth(year, month)
Docs
Dim dateString As String = String.Format("{0} 1 2001", month.SelectedItem)
Dim dDate As Date = DateTime.Parse(dateString)
Dim numberOfMonth As Integer = DateAndTime.Month(dDate)
For jkl = 1 To DateTime.DaysInMonth(numberOfMonth, year.SelectedItem)
day.Items.Add(jkl)
Next

Answer 3

Personally, i would have made a nested If
if month.SelectedItem = "Feb" then
if year.SelectedItem = "2016" Or "2012" Or "2008" Or "2004" Then
Dim jkl As Integer
For jkl = 1 To 29
day.Items.Add(jkl)
Next
else
Dim poi As Integer
For poi = 1 To 28
day.Items.Add("poi")
Next
end if