ant-design/components/date-picker/style/MonthPanel.less

.@{calendar-prefix-cls}-month-panel {
  position: absolute;
  top: 1px;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 10;
  border-radius: @border-radius-base;
  background: @component-background;
  outline: none;

  > div { // TODO: this is a useless wrapper, and we need to remove it in rc-calendar
    height: 100%;
  }
}

.@{calendar-prefix-cls}-month-panel-hidden {
  display: none;
}

.@{calendar-prefix-cls}-month-panel-header {
  .calendarPanelHeader(~"@{calendar-prefix-cls}-month-panel");
}

.@{calendar-prefix-cls}-month-panel-body {
  height: ~"calc(100% - 34px)";
}

.@{calendar-prefix-cls}-month-panel-table {
  table-layout: fixed;
  width: 100%;
  height: 100%;
  border-collapse: separate;
}

.@{calendar-prefix-cls}-month-panel-selected-cell .@{calendar-prefix-cls}-month-panel-month {
  background: @primary-color;
  color: #fff;

  &:hover {
    background: @primary-color;
    color: #fff;
  }
}

.@{calendar-prefix-cls}-month-panel-cell {
  text-align: center;

  &-disabled .@{calendar-prefix-cls}-month-panel-month {
    &,
    &:hover {
      cursor: not-allowed;
      color: #bcbcbc;
      background: @background-color-base;
    }
  }
}

.@{calendar-prefix-cls}-month-panel-month {
  display: inline-block;
  margin: 0 auto;
  color: @text-color;
  background: transparent;
  text-align: center;
  height: 24px;
  line-height: 24px;
  padding: 0 6px;
  border-radius: 4px;
  transition: background 0.3s ease;

  &:hover {
    background: @primary-1;
    cursor: pointer;
  }
}