From e4ef1b2224764e0ca6195676f20d889d0f3c631a Mon Sep 17 00:00:00 2001
From: Samuel Reichert <samuelreichertt@gmail.com>
Date: Fri, 20 Feb 2026 09:10:27 +0100
Subject: [PATCH 1/2] fix(calendar-web): update startDateAttribute to use
 EditableValue and handle null cases

---
 packages/pluggableWidgets/calendar-web/src/Calendar.tsx    | 7 ++++++-
 packages/pluggableWidgets/calendar-web/src/Calendar.xml    | 4 ++--
 .../calendar-web/src/helpers/CalendarPropsBuilder.ts       | 6 +++++-
 .../calendar-web/typings/CalendarProps.d.ts                | 4 ++--
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/packages/pluggableWidgets/calendar-web/src/Calendar.tsx b/packages/pluggableWidgets/calendar-web/src/Calendar.tsx
index a7d8d31d52..e245ee7b34 100644
--- a/packages/pluggableWidgets/calendar-web/src/Calendar.tsx
+++ b/packages/pluggableWidgets/calendar-web/src/Calendar.tsx
@@ -8,7 +8,7 @@ import "./ui/Calendar.scss";
 import { useCalendarEvents } from "./helpers/useCalendarEvents";
 import { useLocalizer } from "./helpers/useLocalizer";
 
-export default function MxCalendar(props: CalendarContainerProps): ReactElement {
+export default function MxCalendar(props: CalendarContainerProps): ReactElement | null {
     // useMemo with empty dependency array is used
     // because style and calendar controller needs to be created only once
     // and not on every re-render
@@ -26,6 +26,11 @@ export default function MxCalendar(props: CalendarContainerProps): ReactElement
     }, [props, calendarController, localizer, culture]);
 
     const calendarEvents = useCalendarEvents(props);
+
+    if (props.startDateAttribute && props.startDateAttribute.status !== "available") {
+        return null;
+    }
+
     return (
         <div className={classNames("widget-calendar", props.class)} style={wrapperStyle}>
             <DnDCalendar {...calendarProps} {...calendarEvents} />
diff --git a/packages/pluggableWidgets/calendar-web/src/Calendar.xml b/packages/pluggableWidgets/calendar-web/src/Calendar.xml
index 0af2436b56..24df8a40ed 100644
--- a/packages/pluggableWidgets/calendar-web/src/Calendar.xml
+++ b/packages/pluggableWidgets/calendar-web/src/Calendar.xml
@@ -62,9 +62,9 @@
                         <attributeType name="String" />
                     </attributeTypes>
                 </property>
-                <property key="startDateAttribute" type="attribute" dataSource="databaseDataSource" required="false">
+                <property key="startDateAttribute" type="attribute" required="false">
                     <caption>Start date attribute</caption>
-                    <description>The start date that should be shown in the view</description>
+                    <description>The DateTime attribute used on initial load</description>
                     <attributeTypes>
                         <attributeType name="DateTime" />
                     </attributeTypes>
diff --git a/packages/pluggableWidgets/calendar-web/src/helpers/CalendarPropsBuilder.ts b/packages/pluggableWidgets/calendar-web/src/helpers/CalendarPropsBuilder.ts
index 6d3c119b8e..d6176e11a6 100644
--- a/packages/pluggableWidgets/calendar-web/src/helpers/CalendarPropsBuilder.ts
+++ b/packages/pluggableWidgets/calendar-web/src/helpers/CalendarPropsBuilder.ts
@@ -16,6 +16,7 @@ export class CalendarPropsBuilder {
     private toolbarItems?: ResolvedToolbarItem[];
     private step: number;
     private timeSlots: number;
+    private defaultDate?: Date;
 
     constructor(private props: CalendarContainerProps) {
         this.isCustomView = props.view === "custom";
@@ -36,6 +37,7 @@ export class CalendarPropsBuilder {
                 `[Calendar] timeslots value ${props.timeslots} was clamped to ${this.timeSlots}. Must be between 1 and 4.`
             );
         }
+        this.defaultDate = props.startDateAttribute?.value;
     }
 
     updateProps(props: CalendarContainerProps): void {
@@ -43,6 +45,7 @@ export class CalendarPropsBuilder {
         this.props = props;
         this.events = this.buildEvents(props.databaseDataSource?.items ?? []);
         this.toolbarItems = this.buildToolbarItems();
+        this.defaultDate = props.startDateAttribute?.value;
     }
 
     build(localizer: DateLocalizer, culture: string): DragAndDropCalendarProps<CalendarEvent> {
@@ -86,7 +89,8 @@ export class CalendarPropsBuilder {
             min: this.minTime,
             max: this.maxTime,
             step: this.step,
-            timeslots: this.timeSlots
+            timeslots: this.timeSlots,
+            ...(this.defaultDate ? { defaultDate: this.defaultDate } : {})
         };
     }
 
diff --git a/packages/pluggableWidgets/calendar-web/typings/CalendarProps.d.ts b/packages/pluggableWidgets/calendar-web/typings/CalendarProps.d.ts
index b0a1628d5e..644e2f5a08 100644
--- a/packages/pluggableWidgets/calendar-web/typings/CalendarProps.d.ts
+++ b/packages/pluggableWidgets/calendar-web/typings/CalendarProps.d.ts
@@ -4,7 +4,7 @@
  * @author Mendix Widgets Framework Team
  */
 import { CSSProperties } from "react";
-import { ActionValue, DynamicValue, ListValue, Option, ListActionValue, ListAttributeValue, ListExpressionValue } from "mendix";
+import { ActionValue, DynamicValue, EditableValue, ListValue, Option, ListActionValue, ListAttributeValue, ListExpressionValue } from "mendix";
 
 export type TitleTypeEnum = "attribute" | "expression";
 
@@ -79,7 +79,7 @@ export interface CalendarContainerProps {
     startAttribute?: ListAttributeValue<Date>;
     endAttribute?: ListAttributeValue<Date>;
     eventColor?: ListAttributeValue<string>;
-    startDateAttribute?: ListAttributeValue<Date>;
+    startDateAttribute?: EditableValue<Date>;
     editable: DynamicValue<boolean>;
     view: ViewEnum;
     defaultViewStandard: DefaultViewStandardEnum;

From d6c5bbadad175dc781f3749450375145f954c5f3 Mon Sep 17 00:00:00 2001
From: Samuel Reichert <samuelreichertt@gmail.com>
Date: Fri, 20 Feb 2026 14:33:53 +0100
Subject: [PATCH 2/2] chore(calendar-web): update changelog

---
 packages/pluggableWidgets/calendar-web/CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/pluggableWidgets/calendar-web/CHANGELOG.md b/packages/pluggableWidgets/calendar-web/CHANGELOG.md
index 4bd6ccc4ac..a2538870ad 100644
--- a/packages/pluggableWidgets/calendar-web/CHANGELOG.md
+++ b/packages/pluggableWidgets/calendar-web/CHANGELOG.md
@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Fixed
+
+- Improved handling of the start date attribute to ensure correct calendar initialization.
+
 ## [2.3.0] - 2026-02-17
 
 ### Added