element-ui/examples/demo-styles/datetime-picker.scss

.demo-block.demo-datetime-picker .source > div {
  padding: 0;
  display: flex;
}

.demo-datetime-picker .block {
  padding: 30px 0;
  text-align: center;
  border-right: solid 1px #eff2f6;
  flex: 1;
  &:last-child {
    border-right: none;
  }
}

.demo-datetime-picker .demonstration {
  display: block;
  color: #8492a6;
  font-size: 14px;
  margin-bottom: 20px;
}