x-antd-vue/es/date-picker/style/MonthPicker.less

base on antd 1.7.2

.@{calendar-prefix-cls}-month {
  .@{calendar-prefix-cls}-month-header-wrap {
    position: relative;
    height: 288px;
  }
  .@{calendar-prefix-cls}-month-panel,
  .@{calendar-prefix-cls}-year-panel {
    top: 0;
    height: 100%;
  }
}