Solved it. I just had to convert the DTSTART and DTEND to ("yyyyMMddTHHmmssZ")
Like this
"DTSTART:" + calEventDateAndTime.ToUniversalTime().ToString("yyyyMMddTHHmmssZ"),
"DTEND:" + calEventDateAndTime.AddMinutes(30).ToUniversalTime().ToString("yyyyMMddTHHmmssZ"),
Thanks