@mixin reset() {
  background: #fff;
  color: #000;
  text-shadow: none;
  height: auto;
  width: auto;
  padding: 0;
  line-height: normal;
  box-shadow: none;
  border-radius: 0;
  font-family: sans-serif;
  font-size: 14px;
}

date-input-polyfill {
  @include reset();
  position: absolute !important;
  border: 1px solid #c0c0c0 !important;
  text-align: center;
  z-index: 1;
  
  select, table, th, td {
    @include reset();
    border: 0;
  }
  select {  
    margin: 3px 5px;
    border: 1px solid #c0c0c0;
  }

  th, td {
    width: 14%;
    padding: 4px;
    text-align: center;
  }

  td {
    cursor: pointer;
  }
  
  .selected {
    font-weight: bold;
  }
}
@mixin reset() {
  background: #fff;
  color: #000;
  text-shadow: none;
  height: auto;
  width: auto;
  padding: 0;
  line-height: normal;
  box-shadow: none;
  border-radius: 0;
  font-family: sans-serif;
  font-size: 14px;
}

date-input-polyfill {
  @include reset();
  position: absolute !important;
  border: 1px solid #c0c0c0;
  text-align: center;
  z-index: 1;
  
  select, table, th, td {
    @include reset();
    border: 0;
  }
  select {  
    margin: 3px 5px;
    border: 1px solid #c0c0c0;
  }

  th, td {
    width: 14%;
    padding: 4px;
    text-align: center;
  }

  td {
    cursor: pointer;
  }
  
  .selected {
    font-weight: bold;
  }
}
Remove important override from picker border.
Remove important override from picker border.
