Dcat-Admin/resources/assets/dcat/sass/components/_datetime-picker.scss

.bootstrap-datetimepicker-widget table td span, .bootstrap-datetimepicker-widget table td i {
  height: 0!important;
  line-height: 0!important;
}

.bootstrap-datetimepicker-widget table td.active, .bootstrap-datetimepicker-widget table td.active:hover {
  background-color: $light!important;
  color: $primary-darker!important;
  font-weight: bold;
}