--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/libcalendaring/lib/Sabre/VObject/Component/VTodo.php	Sat Jan 13 08:57:56 2018 -0500
@@ -0,0 +1,68 @@
+<?php
+
+namespace Sabre\VObject\Component;
+
+use Sabre\VObject;
+
+/**
+ * VTodo component
+ *
+ * This component contains some additional functionality specific for VTODOs.
+ *
+ * @copyright Copyright (C) 2007-2013 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
+ */
+class VTodo extends VObject\Component {
+
+    /**
+     * Returns true or false depending on if the event falls in the specified
+     * time-range. This is used for filtering purposes.
+     *
+     * The rules used to determine if an event falls within the specified
+     * time-range is based on the CalDAV specification.
+     *
+     * @param DateTime $start
+     * @param DateTime $end
+     * @return bool
+     */
+    public function isInTimeRange(\DateTime $start, \DateTime $end) {
+
+        $dtstart = isset($this->DTSTART)?$this->DTSTART->getDateTime():null;
+        $duration = isset($this->DURATION)?VObject\DateTimeParser::parseDuration($this->DURATION):null;
+        $due = isset($this->DUE)?$this->DUE->getDateTime():null;
+        $completed = isset($this->COMPLETED)?$this->COMPLETED->getDateTime():null;
+        $created = isset($this->CREATED)?$this->CREATED->getDateTime():null;
+
+        if ($dtstart) {
+            if ($duration) {
+                $effectiveEnd = clone $dtstart;
+                $effectiveEnd->add($duration);
+                return $start <= $effectiveEnd && $end > $dtstart;
+            } elseif ($due) {
+                return
+                    ($start < $due || $start <= $dtstart) &&
+                    ($end > $dtstart || $end >= $due);
+            } else {
+                return $start <= $dtstart && $end > $dtstart;
+            }
+        }
+        if ($due) {
+            return ($start < $due && $end >= $due);
+        }
+        if ($completed && $created) {
+            return
+                ($start <= $created || $start <= $completed) &&
+                ($end >= $created || $end >= $completed);
+        }
+        if ($completed) {
+            return ($start <= $completed && $end >= $completed);
+        }
+        if ($created) {
+            return ($end > $created);
+        }
+        return true;
+
+    }
+
+}