Comparing dates with a function if/else statement

I'm a relatively new web developer who has recently inherited a client web site that features the following code:

<%
    If objDbRs("Accred_Date") <> "" Then
    dim dateAcc, dateAccEnd
    dateAcc = formatDateTime(objDbRs("Accred_Date"),vbshortdate)
    dateAccEnd = DateAdd("yyyy",5,dateAcc)

    Response.write dateAcc & " to " & dateAccEnd
Else
    Response.write "<em>Accreditation information not available.</em>"
End If
%>

It simply displays a given profile's sign up date and an expiration date coded for 5 years later. The client has asked my company to change this automated expiration date to 3 years later, rather than 5. However, this should only affect the profiles that were added on or after June 1, 2016, leaving all of the older profiles grandfathered in for 5 years.

I am not immediately familiar with this code or its syntax and was hoping to get some help in resolving this issue. If someone could show me what code adjustments are necessary to accomplish this objective AND provide a useful syntax reference source for this language, so that I can better handle similar client requests in the future, I'd greatly appreciate it.