diff --git a/calendar/inc/class.calendar_owner_etemplate_widget.inc.php b/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
index 9129487214..196ee1584e 100644
--- a/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
+++ b/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
@@ -151,7 +151,7 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 			$labels = Array();
 			foreach($id as $index => $_id)
 			{
-				$labels[$_id] = self::get_owner_label($_id);
+				$labels[$_id] = self::format_owner($_id, self::get_owner_label($_id));
 			}
 			Api\Json\Response::get()->data($labels);
 			return $labels;
@@ -232,38 +232,7 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 			{
 				if($id && $title)
 				{
-					// Magicsuggest uses id, not value.
-					$value = array(
-						'id' => $type.$id,
-						'value'=> $type.$id,
-						'label' => $title,
-						'app'	=> lang($data['app'])
-					);
-					if(is_array($value['label']))
-					{
-						$value = array_merge($value, $value['label']);
-					}
-					switch($type)
-					{
-						case 'r':
-							// TODO: fetch resources photo
-							break;
-						case 'c':
-						case '':
-							$contact = $contacts_obj->read($type === '' ? 'account:'.$id : $id, true);
-							if (is_array($contact)) $value['icon'] = Api\Framework::link('/api/avatar.php', array(
-								'contact_id' => $contact['id'],
-								'etag' => $contact['etag'] ? $contact['etag'] : 1
-							));
-							if($id < 0)
-							{
-								$value['resources'] = array_map('strval',$GLOBALS['egw']->accounts->members($id, true));
-							}
-							break;
-						default :
-							// do nothing
-					}
-					$mapped[] = $value;
+					$mapped[] = static::format_owner($id, $title, $data);
 				}
 			}
 			if(count($mapped))
@@ -280,6 +249,68 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 		exit();
 	}
 
+	/**
+	 * Given an ID & title, format the result into data the client side wants
+	 *
+	 * @param $id
+	 * @param $title
+	 * @param $type
+	 */
+	protected static function format_owner($id, $title, $data = array())
+	{
+		static $contacts_obj = null;
+		if(is_null($contacts_obj))
+		{
+			$contacts_obj = new Api\Contacts();
+		}
+		if(!$data)
+		{
+			$bo = new calendar_bo();
+			if(!is_numeric($id))
+			{
+				$data = $bo->resources[substr($id, 0, 1)];
+			}
+			else
+			{
+				$data = $bo->resources[''];
+			}
+		}
+		$type = $data['type'];
+
+		// Magicsuggest uses id, not value.
+		$value = array(
+			'id' => $type.$id,
+			'value'=> $type.$id,
+			'label' => $title,
+			'app'	=> lang($data['app'])
+		);
+		if(is_array($value['label']))
+		{
+			$value = array_merge($value, $value['label']);
+		}
+		switch($type)
+		{
+			case 'r':
+				// TODO: fetch resources photo
+				break;
+			case 'c':
+			case '':
+				$contact = $contacts_obj->read($type === '' ? 'account:'.$id : $id, true);
+				if (is_array($contact)) $value['icon'] = Api\Framework::link('/api/avatar.php', array(
+					'contact_id' => $contact['id'],
+					'etag' => $contact['etag'] ? $contact['etag'] : 1
+				));
+				if($id < 0)
+				{
+					$value['resources'] = array_map('strval',$GLOBALS['egw']->accounts->members($id, true));
+				}
+				break;
+			default :
+				// do nothing
+		}
+		return $value;
+	}
+
 	/**
 	 * Get just the label for a single owner
 	 * @param string $id
diff --git a/calendar/js/et2_widget_daycol.js b/calendar/js/et2_widget_daycol.js
index 77102101cf..1f0ab645d0 100644
--- a/calendar/js/et2_widget_daycol.js
+++ b/calendar/js/et2_widget_daycol.js
@@ -96,9 +96,9 @@ var et2_calendar_daycol = /** @class */ (function (_super) {
         if (this.title.text() === '' && this.options.date &&
             this.getParent() && this.getParent().instanceOf(et2_widget_timegrid_1.et2_calendar_timegrid)) {
             // Forces an update
-            var date_1 = this.options.date;
+            var date = this.options.date;
             this.options.date = '';
-            this.set_date(date_1);
+            this.set_date(date);
         }
         return result;
     };
diff --git a/calendar/js/et2_widget_owner.js b/calendar/js/et2_widget_owner.js
index c9ce765a79..3d2b0f0a69 100644
--- a/calendar/js/et2_widget_owner.js
+++ b/calendar/js/et2_widget_owner.js
@@ -115,8 +115,10 @@ var et2_calendar_owner = /** @class */ (function (_super) {
                         return "continue";
                     var idx = this_1.options.value.find(function (element) { return element.id == owner; });
                     if (idx) {
-                        idx.label = data[owner];
+                        idx = jQuery.extend(idx, data[owner]);
                     }
+                    // Put it in the list of options for next time
+                    this_1.options.select_options.push(data[owner]);
                 };
                 var this_1 = this;
                 for (var owner in data) {
diff --git a/calendar/js/et2_widget_owner.ts b/calendar/js/et2_widget_owner.ts
index 5e971975a2..35eadd18a4 100644
--- a/calendar/js/et2_widget_owner.ts
+++ b/calendar/js/et2_widget_owner.ts
@@ -139,8 +139,10 @@ export class et2_calendar_owner extends et2_taglist_email
 					let idx = this.options.value.find(element => element.id == owner);
 					if(idx)
 					{
-						idx.label = data[owner];
+						idx = jQuery.extend(idx, data[owner]);
 					}
+					// Put it in the list of options for next time
+					this.options.select_options.push(data[owner]);
 				}
 				this.set_value(this.options.value);
 			}, this,true,this).sendRequest();
diff --git a/calendar/js/et2_widget_planner.js b/calendar/js/et2_widget_planner.js
index be49999535..0715a04a7a 100644
--- a/calendar/js/et2_widget_planner.js
+++ b/calendar/js/et2_widget_planner.js
@@ -118,7 +118,13 @@ var et2_calendar_planner = /** @class */ (function (_super) {
                                     }
                                 }
                             }
-                            else if (already_added.indexOf('' + user) < 0) {
+                            else if (user < 0) {
+                                // Group, but no users found.  Need those.
+                                egw.accountData(parseInt(user), 'account_fullname', true, function (result) {
+                                    this.invalidate();
+                                }, this);
+                            }
+                            else if (already_added.indexOf('' + user) < 0 && parseInt(user) >= 0) {
                                 labels.push({
                                     id: user,
                                     label: this._get_owner_name(user),
@@ -1628,6 +1634,63 @@ var et2_calendar_planner = /** @class */ (function (_super) {
             this.invalidate(true);
         }
     };
+    /**
+     * Set which users to display
+     *
+     * Changing the owner will invalidate the display, and it will be redrawn
+     * after a timeout.  Overwriting here to check for groups without members.
+     *
+     * @param {number|number[]|string|string[]} _owner - Owner ID, which can
+     *	be an account ID, a resource ID (as defined in calendar_bo, not
+     *	necessarily an entry from the resource app), or a list containing a
+     *	combination of both.
+     *
+     * @memberOf et2_calendar_view
+     */
+    et2_calendar_planner.prototype.set_owner = function (_owner) {
+        _super.prototype.set_owner.call(this, _owner);
+        // If we're grouping by user, we need group members
+        if (this.update_timer !== null && this.options.group_by == 'user') {
+            var options_1 = [];
+            var resource = {};
+            var missing_resources_1 = [];
+            if (app.calendar && app.calendar.sidebox_et2 && app.calendar.sidebox_et2.getWidgetById('owner')) {
+                options_1 = app.calendar.sidebox_et2.getWidgetById('owner').taglist.getSelection();
+            }
+            else {
+                options_1 = this.getArrayMgr("sel_options").getRoot().getEntry('owner');
+            }
+            for (var i = 0; i < this.options.owner.length; i++) {
+                var user = this.options.owner[i];
+                if (isNaN(user) || user >= 0 || !options_1)
+                    continue;
+                // Owner is a group, see if we have its members
+                if (options_1.find &&
+                    ((resource = options_1.find(function (element) {
+                        return element.id == user;
+                    })))) {
+                    // Members found
+                    continue;
+                }
+                // Group, but no users found.  Need those.
+                missing_resources_1.push(user);
+                // Maybe api already has them?
+                egw.accountData(parseInt(user), 'account_fullname', true, function (result) {
+                    missing_resources_1.splice(missing_resources_1.indexOf(this), 1);
+                }.bind(user), user);
+            }
+            if (missing_resources_1.length > 0) {
+                // Ask server, and WAIT or we have to redraw
+                egw.json('calendar_owner_etemplate_widget::ajax_owner', [missing_resources_1], function (data) {
+                    for (var owner in data) {
+                        if (!owner || typeof owner == "undefined")
+                            continue;
+                        options_1.push(data[owner]);
+                    }
+                }, this, false, this).sendRequest(false);
+            }
+        }
+    };
     /**
      * Turn on or off the visibility of weekends
      *
diff --git a/calendar/js/et2_widget_planner.ts b/calendar/js/et2_widget_planner.ts
index ab041f5df6..9a69a4be3c 100644
--- a/calendar/js/et2_widget_planner.ts
+++ b/calendar/js/et2_widget_planner.ts
@@ -446,7 +446,14 @@ export class et2_calendar_planner extends et2_calendar_view implements et2_IDeta
 								}
 							}
 						}
-						else if(already_added.indexOf(''+user) < 0)
+						else if (user < 0)
+						{
+							// Group, but no users found.  Need those.
+							egw.accountData(parseInt(user),'account_fullname',true,function(result) {
+								this.invalidate();
+							},this);
+						}
+						else if(already_added.indexOf(''+user) < 0 && parseInt(user) >= 0)
 						{
 							labels.push({
 								id: user,
@@ -2093,6 +2100,75 @@ export class et2_calendar_planner extends et2_calendar_view implements et2_IDeta
 		}
 	}
 
+	/**
+	 * Set which users to display
+	 *
+	 * Changing the owner will invalidate the display, and it will be redrawn
+	 * after a timeout.  Overwriting here to check for groups without members.
+	 *
+	 * @param {number|number[]|string|string[]} _owner - Owner ID, which can
+	 *	be an account ID, a resource ID (as defined in calendar_bo, not
+	 *	necessarily an entry from the resource app), or a list containing a
+	 *	combination of both.
+	 *
+	 * @memberOf et2_calendar_view
+	 */
+	set_owner(_owner)
+	{
+		super.set_owner(_owner);
+
+		// If we're grouping by user, we need group members
+		if(this.update_timer !== null && this.options.group_by == 'user')
+		{
+			let options = [];
+			let resource = {};
+			let missing_resources = [];
+
+			if(app.calendar && app.calendar.sidebox_et2 && app.calendar.sidebox_et2.getWidgetById('owner'))
+			{
+				options = app.calendar.sidebox_et2.getWidgetById('owner').taglist.getSelection();
+			}
+			else
+			{
+				options = this.getArrayMgr("sel_options").getRoot().getEntry('owner');
+			}
+			for(var i = 0; i < this.options.owner.length; i++)
+			{
+				var user = this.options.owner[i];
+				if(isNaN(user) || user >= 0 || !options) continue;
+
+				// Owner is a group, see if we have its members
+				if(options.find &&
+					((resource = options.find(function (element)
+                      {
+                          return element.id == user;
+                      }))))
+				{
+					// Members found
+					continue;
+				}
+				// Group, but no users found.  Need those.
+				missing_resources.push(user);
+
+				// Maybe api already has them?
+				egw.accountData(parseInt(user),'account_fullname',true,function(result) {
+					missing_resources.splice(missing_resources.indexOf(this),1);
+				}.bind(user),user);
+			}
+			if(missing_resources.length > 0)
+			{
+				// Ask server, and WAIT or we have to redraw
+				egw.json('calendar_owner_etemplate_widget::ajax_owner',[missing_resources],function(data) {
+					for(let owner in data)
+					{
+						if(!owner || typeof owner == "undefined") continue;
+						options.push(data[owner]);
+					}
+				}, this,false,this).sendRequest(false);
+			}
+		}
+	}
+
 	/**
 	 * Turn on or off the visibility of weekends
 	 *