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

.d-date-time-input-range {
  padding: 0.5em;
  background: whitesmole;
  border: 1px solid $primary-low;
  width: 300px;
  display: flex;
  flex-direction: column;

  .panels {
    display: inline-flex;
    list-style: none;
    margin: 0 0 0.5em 0;
    flex: 1;

    &.from {
      .from-panel {
        background: $danger;
        color: $secondary;
      }
    }

    &.to {
      .to-panel {
        background: $danger;
        color: $secondary;
      }
    }

    .btn {
      margin-right: 0.5em;
    }
  }

  .panel {
    display: none;
    flex: 1;

    &.visible {
      display: flex;
    }
  }
}