.exams {
  text-align: center;
}
.exam_date {
  text-decoration: none;
  border: 1px solid green;
  padding: 7px 17px;
  border-radius: 20px;
  color: white;
  background-color: green;
  display: inline-block;
}

.exam_date:hover {
  padding: 7px 17px;
  border-radius: 20px;
  color: green;
  background-color: white;
}