if you think internet connection is available where your .exe is going to be run.
then you can make a web request "http://www.timeapi.org/utc/now.json" it will return you current date and time. then you can compare this date with your build date and disable your .exe.
the advantage of this is
1 : it will insure that your .exe file will not work after 30 days. even user has refreshed windows cause it is PC independent.
2 : the above solution fails if user change the date time or set to early days just exception
cause your current date time is the local date time of the PC
how to make a web request in c# ?
var http = (HttpWebRequest)WebRequest.Create("http://www.timeapi.org/utc/now.json");
var response = http.GetResponse();
var stream = response.GetResponseStream();
var sr = new StreamReader(stream);
var jsonCurrentDate= sr.ReadToEnd();