An example SS_Report for LastLoggedIn.

LastLoggedInReport.php

<?php

class LastLoggedInReport extends SS_Report {

  public function title() {
		if(isset($_GET['ago'])) {
			$ago = (int) $_GET['ago'];

			return "Last logged in $ago months ago";
		}

		return "Last logged in ago..";
	}

	public function records($params = null) {
		$records = new ArrayList();

		if(isset($_GET['date'])) {
			list($month, $year) = explode('-', $_GET['date']);

			$agents = Group::get()->filter(array(
				'Code' => 'users'
			))->first();

			$agentsId = $agents->ID;

			$data = Member::get()->where(array(
				"EXTRACT(YEAR FROM LastVisited) = '$year' 
					AND EXTRACT(MONTH FROM LastVisited) = '$month'
					AND Group_Members.GroupID = '$agentsId'" 
			))->exclude(array(
				'TestAgent' => 1
			))->innerJoin("Group_Members", "Member.ID = Group_Members.MemberID")
			->sort('LastVisited ASC');
		
			return $data;
		}


		for($i = 0; $i <= 24; $i++) {
			$t = strtotime("-$i MONTH");
			$year = date('Y', $t);
			$month = date('m', $t);

			$records->push(new ReportsDataRow(array(
				'Title' => date('F Y', $t),
				'Date' => date('m-Y', $t),
				'I' => $i,
				'Count' => DB::query("
					SELECT COUNT(*) 
					FROM Member 
					WHERE EXTRACT(YEAR FROM LastVisited) = '$year' AND EXTRACT(MONTH FROM LastVisited) = '$month'"
				)->value()
			)));
		}

		return $records;
	}

	public function sourceRecords($params = null) {
		return $this->records();
	}

	public function getReportField() {
		$field = parent::getReportField();
		$field->getConfig()->getComponentByType('GridFieldPaginator')->setItemsPerPage(2000);
		
		return $field;
	}

	public function columns() {
		if(isset($_GET['ago'])) {
			return array(
				'FirstName' => array(
					"formatting" => '<a href=\"users/show/$UrlHash/$Slug\">$value</a>'
				),
				'Surname' => array(),
				'Email' => array(),
			);
		}
		else {
			return array(
				"Title" => array(
					"title" => "Last logged in months ago..",
					'formatting' => '<a href=\"admin/reports/LastLoggedInReport/?date=$Date&ago=$I\">$I months ago</a>'
				),
				"Count" => array()
			);
		}
	}

ReportsDataRow.php

<?php

class ReportsDataRow extends ArrayData {

	public function canView() {
		return true;
	}
}