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

.@{calendar-prefix-cls}-picker-container {
  position: absolute;
  z-index: @zindex-picker;

  &.slide-up-enter.slide-up-enter-active&-placement-topLeft,
  &.slide-up-enter.slide-up-enter-active&-placement-topRight,
  &.slide-up-appear.slide-up-appear-active&-placement-topLeft,
  &.slide-up-appear.slide-up-appear-active&-placement-topRight {
    animation-name: antSlideDownIn;
  }

  &.slide-up-enter.slide-up-enter-active&-placement-bottomLeft,
  &.slide-up-enter.slide-up-enter-active&-placement-bottomRight,
  &.slide-up-appear.slide-up-appear-active&-placement-bottomLeft,
  &.slide-up-appear.slide-up-appear-active&-placement-bottomRight {
    animation-name: antSlideUpIn;
  }

  &.slide-up-leave.slide-up-leave-active&-placement-topLeft,
  &.slide-up-leave.slide-up-leave-active&-placement-topRight {
    animation-name: antSlideDownOut;
  }

  &.slide-up-leave.slide-up-leave-active&-placement-bottomLeft,
  &.slide-up-leave.slide-up-leave-active&-placement-bottomRight {
    animation-name: antSlideUpOut;
  }
}

.@{calendar-prefix-cls}-picker {
  position: relative;
  display: inline-block;
  outline: none;
  font-size: @font-size-base;
  transition: opacity 0.3s;

  &-input {
    outline: none;
  }

  &:hover &-input {
    border-color: @primary-color;
  }

  &-clear {
    opacity: 0;
    pointer-events: none;
    z-index: 1;
    position: absolute;
    right: 7px;
    background: #fff;
    top: 50%;
    font-size: @font-size-base;
    color: @disabled-color;
    width: 14px;
    height: 14px;
    margin-top: -7px;
    line-height: 14px;
    cursor: pointer;
    transition: color 0.3s, opacity 0.3s;
    &:hover {
      color: @text-color-secondary;
    }
  }

  &:hover &-clear {
    opacity: 1;
    pointer-events: auto;
  }

  &-icon {
    position: absolute;
    user-select: none;
    transition: all .3s;
    width: 12px;
    height: 12px;
    line-height: 12px;
    right: 8px;
    color: @text-color-secondary;
    top: 50%;
    margin-top: -6px;
    &:after {
      content: "\e6bb";
      font-family: "anticon";
      font-size: @font-size-base;
      color: @text-color-secondary;
      display: inline-block;
      line-height: 1;
      vertical-align: bottom;
    }
  }
}