discourse/app/assets/stylesheets/common/components/date-input.scss

.d-date-input {
  display: flex;
  flex: 1;
  cursor: pointer;
  flex-direction: column;

  .date-picker {
    cursor: pointer;
    margin: 0;
    text-align: left;
    width: 100%;
    outline: none;
    box-shadow: none !important;
  }

  .pika-single {
    margin-left: -1px;
  }
}