date filter is not actually filtering

<?php
//application functions

function get_project_list() {
  include 'connection.php';

  try {
    return $db->query('SELECT project_id, title, category FROM projects');
  } catch (Exception $e) {
    echo "Error: " . $e->getMessage() . "</br>";
    return array();
  }
}

function get_task_list($filter = null) {
  include 'connection.php';

  $sql = 'SELECT tasks.*, projects.title as project FROM tasks'
  . ' JOIN projects ON tasks.project_id = projects.project_id';

  $where = '';
  if (is_array($filter)) {
    switch ($filter[0]) {
      case 'project':
        $where = ' WHERE projects.project_id = ?';
        break;
      case 'category':
        $where = ' WHERE category = ?';
        break;
      case 'date':
        $where = ' WHERE date >= ? AND date <= ?';
    }
  }

  $orderBy = ' ORDER BY date DESC';
  if ($filter) {
    $orderBy = ' ORDER BY projects.title ASC, date DESC';
  }

  try {
    $results = $db->prepare($sql . $where . $orderBy);
    if (is_array($filter)) {
      $results->bindValue(1, $filter[1]);
      if ($filter[0] == 'date') {
        $results->bindValue(2, $filter[2], PDO::PARAM_STR);
      }
    }
    $results->execute();
  } catch (Exception $e) {
    echo "Error: " . $e->getMessage() . "</br>";
    return array();
  }
  return $results->fetchAll(PDO::FETCH_ASSOC);
}


function add_project($title, $category) {
  include 'connection.php';

  $sql = 'INSERT INTO projects(title, category) VALUES(?, ?)';

  try {
    $results = $db->prepare($sql);
    $results->bindValue(1, $title, PDO::PARAM_STR);
    $results->bindValue(2, $category, PDO::PARAM_STR);
    $results->execute();
  } catch (Exception $e) {
    echo "Error: " . $e->getMessage() . "<br />";
    return false;
  }
  return true;
}

function add_task($project_id, $title, $date, $time) {
  include 'connection.php';

  $sql = 'INSERT INTO tasks(project_id, title, date, time) VALUES(?, ?, ?, ?)';

  try {
    $results = $db->prepare($sql);
    $results->bindValue(1, $project_id, PDO::PARAM_INT);
    $results->bindValue(2, $title, PDO::PARAM_STR);
    $results->bindValue(3, $date, PDO::PARAM_STR);
    $results->bindValue(4, $time, PDO::PARAM_INT);
    $results->execute();
  } catch (Exception $e) {
    echo "Error: " . $e->getMessage() . "<br />";
    return false;
  }
  return true;
}

<?php
require 'inc/functions.php';

$page = "reports";
$pageTitle = "Reports | Time Tracker";
$filter = "all";

if (!empty($_GET['filter'])) {
  $filter = explode(':', filter_input(INPUT_GET, 'filter', FILTER_SANITIZE_STRING));
}

include 'inc/header.php';
?>
<div class="col-container page-container">
    <div class="col col-70-md col-60-lg col-center">
        <div class="col-container">
            <h1 class='actions-header'>Reports</h1>
          <form class='form-container form-report' action='reports.php' method='get'>
            <label for='filter'>Filter:</label>
            <select id='filter' name='filter'>
              <option value=''>Select One</option>
              <optgroup label="Project">
              <?php
              foreach(get_project_list() as $item) {
                echo '<option value="project:' . $item['project_id'] . '">';
                echo $item['title'] . "</option>\n";
              }
              ?>
              </optgroup>
              <optgroup label="Category">
                <option value="category:Billable">Billable</option>
                <option value="category:Charity">Charity</option>
                <option value="category:Personal">Personal</option>
              </optgroup>
              <optgroup label="Date">
                <option value="date:<?php
                  echo date('m/d/Y',strtotime('-2 Sunday'));
                  echo ":";
                  echo date('m/d/Y',strtotime('-1 Saturday'));
                ?>">Last Week</option>
                <option value="date:
                <?php
                  echo date('m/d/Y',strtotime('-1 Sunday'));
                  echo ":";
                  echo date('m/d/Y');
                ?>">This Week</option>
                <option value="date:
                <?php
                  echo date('m/d/Y',strtotime('first day of last month'));
                  echo ":";
                  echo date('m/d/Y',strtotime('last day of last month'));
                ?>">Last Month</option>
                <option value="date:
                <?php
                  echo date('m/d/Y',strtotime('first day of this month'));
                  echo ":";
                  echo date('m/d/Y');
                ?>">This Month</option>
              </optgroup>
            </select>
            <input class="button" type="submit" value="Run" />
          </form>
        </div>
        <div class="section page">
            <div class="wrapper">
                <table>
                  <?php
                  $total = $project_id = $project_total = 0;
                  $tasks = get_task_list($filter);
                  foreach ($tasks as $item) {
                    if ($project_id != $item['project_id']) {

                      $project_id = $item['project_id'];
                      echo "<thead>\n";
                      echo "<tr>\n";
                      echo "<th>" . $item['project'] . "</th>\n";
                      echo "<th>Date</th>\n";
                      echo "<th>Time</th>\n";
                      echo "</tr>\n";
                      echo "</thead>\n";
                    }
                    $project_total += $item['time'];
                    $total += $item['time'];
                    echo "<tr>\n";
                    echo "<td>" . $item['title'] . "</td>\n";
                    echo "<td>" . $item['date'] . "</td>\n";
                    echo "<td>" . $item['time'] . "</td>\n";
                    echo "</tr>\n";
                    if (next($tasks)['project_id'] != $item['project_id']) {
                        echo "<tr>\n";
                        echo "<th class = 'project-total-label' colspan = '2'>Project Total</th>\n";
                        echo "<th class= 'project-total-number'>$project_total</th>\n";
                        echo "</tr>\n";
                        $project_total = 0;
                      }
                  }
                  ?>
                    <tr>
                        <th class='grand-total-label' colspan='2'>Grand Total</th>
                        <th class='grand-total-number'><?php echo $total; ?></th>
                    </tr>
                </table>
            </div>
        </div>
    </div>
</div>

<?php include "inc/footer.php"; ?>