feat(#1108): Add option to use task duration for ICS export event length

When enabled, exported calendar events use scheduled date + time estimate
as DTSTART/DTEND instead of using due date for DTEND.

This aligns with GTD workflows where scheduled + duration represents work
planning, while due date represents deadlines. The feature is off by default
to preserve existing behavior.

- Add useDurationForExport setting to ICSIntegrationSettings
- Add ICSExportOptions interface for export configuration
- Update CalendarExportService methods to accept duration option
- Add UI toggle in Settings → Integrations → Automatic ICS Export
- Add English translation keys for the new setting
- Update and enable tests for the feature

Author: callumalpass

docs/releases/unreleased.md

@@ -99,6 +99,13 @@ Example:
   - Defaults to disabled to preserve existing behavior
   - Thanks to @MiserMagus for the feature request
 
+- (#1108) Option to use task duration instead of due date for ICS calendar export
+  - New "Use task duration for event length" toggle in Settings → Integrations → Automatic ICS Export
+  - When enabled, exported calendar events use scheduled date + time estimate as DTSTART/DTEND
+  - This aligns with GTD workflows where scheduled + duration represents work planning, while due date represents deadlines
+  - When disabled (default), preserves existing behavior using due date as DTEND
+  - Thanks to @bepolymathe for the feature request
+
 ## Fixed
 
 - (#1384) Fixed title being sanitized even when "Store Task Title in Filename" is disabled

src/i18n/resources/en.ts

@@ -1677,6 +1677,11 @@ export const en: TranslationTree = {
 					description: "How often to update the export file",
 					placeholder: "60",
 				},
+				useDuration: {
+					name: "Use task duration for event length",
+					description:
+						"When enabled, uses the task's time estimate (duration) instead of due date for the calendar event end time. This is useful for GTD workflows where scheduled + duration represents work planning, while due date represents deadlines.",
+				},
 				exportNow: {
 					name: "Export now",
 					description: "Manually trigger an immediate export",

src/services/AutoExportService.ts

@@ -100,8 +100,11 @@ export class AutoExportService {
 				return;
 			}
 
-			// Generate ICS content
-			const icsContent = CalendarExportService.generateMultipleTasksICSContent(allTasks);
+			// Generate ICS content with export options from settings
+			const exportOptions = {
+				useDurationForExport: this.plugin.settings.icsIntegration.useDurationForExport,
+			};
+			const icsContent = CalendarExportService.generateMultipleTasksICSContent(allTasks, exportOptions);
 
 			// Write to file - use path as-is since Obsidian handles normalization
 			const normalizedPath = exportPath;

src/services/CalendarExportService.ts

@@ -9,6 +9,10 @@ export interface CalendarURLOptions {
 	useScheduledAsDue?: boolean; // If task has no due date, use scheduled as end time
 }
 
+export interface ICSExportOptions {
+	useDurationForExport?: boolean; // Use timeEstimate (duration) instead of due date for DTEND
+}
+
 type TranslateFn = (key: TranslationKey, variables?: Record<string, any>) => string;
 
 export class CalendarExportService {
@@ -162,7 +166,7 @@ export class CalendarExportService {
 	/**
 	 * Generate ICS file content
 	 */
-	static generateICSContent(task: TaskInfo): string {
+	static generateICSContent(task: TaskInfo, options?: ICSExportOptions): string {
 		const uid = `${task.path.replace(/[^a-zA-Z0-9]/g, "-")}-${Date.now()}@tasknotes`;
 		const now = new Date()
 			.toISOString()
@@ -184,7 +188,7 @@ export class CalendarExportService {
 		lines.push(`SUMMARY:${this.escapeICSText(task.title)}`);
 
 		// Add dates
-		const { startICS, endICS } = this.getICSDateFormat(task);
+		const { startICS, endICS } = this.getICSDateFormat(task, true, options);
 		if (startICS) {
 			lines.push(`DTSTART:${startICS}`);
 		}
@@ -309,7 +313,8 @@ export class CalendarExportService {
 	 */
 	private static getTaskDateRange(
 		task: TaskInfo,
-		useScheduledAsDue: boolean
+		useScheduledAsDue: boolean,
+		options?: ICSExportOptions
 	): { startISO: string | null; endISO: string | null } {
 		let startISO: string | null = null;
 		let endISO: string | null = null;
@@ -323,15 +328,22 @@ export class CalendarExportService {
 			}
 		}
 
-		if (task.due) {
+		// When useDurationForExport is enabled, use timeEstimate to calculate end time
+		// instead of using due date
+		if (options?.useDurationForExport && startISO && task.timeEstimate && task.timeEstimate > 0) {
+			// Use scheduled + timeEstimate (in minutes) as end time
+			const start = new Date(startISO);
+			const end = new Date(start.getTime() + task.timeEstimate * 60 * 1000);
+			endISO = end.toISOString();
+		} else if (task.due) {
 			try {
 				const dueDate = this.parseTaskDate(task.due);
 				endISO = dueDate.toISOString();
 			} catch (e) {
 				console.warn("Invalid due date:", task.due);
 			}
 		} else if (useScheduledAsDue && startISO) {
-			// Use scheduled + 1 hour as end time
+			// Use scheduled + 1 hour as end time (default fallback)
 			const start = new Date(startISO);
 			const end = new Date(start.getTime() + 60 * 60 * 1000);
 			endISO = end.toISOString();
@@ -365,9 +377,10 @@ export class CalendarExportService {
 	 */
 	private static getICSDateFormat(
 		task: TaskInfo,
-		useScheduledAsDue = true
+		useScheduledAsDue = true,
+		options?: ICSExportOptions
 	): { startICS: string | null; endICS: string | null } {
-		const { startISO, endISO } = this.getTaskDateRange(task, useScheduledAsDue);
+		const { startISO, endISO } = this.getTaskDateRange(task, useScheduledAsDue, options);
 
 		const formatICS = (isoString: string): string => {
 			const date = new Date(isoString);
@@ -460,7 +473,7 @@ export class CalendarExportService {
 	/**
 	 * Generate ICS content for multiple tasks
 	 */
-	static generateMultipleTasksICSContent(tasks: TaskInfo[]): string {
+	static generateMultipleTasksICSContent(tasks: TaskInfo[], options?: ICSExportOptions): string {
 		const now = new Date()
 			.toISOString()
 			.replace(/[-:]/g, "")
@@ -485,7 +498,7 @@ export class CalendarExportService {
 			lines.push(`SUMMARY:${this.escapeICSText(task.title)}`);
 
 			// Add dates - ensure every event has a DTSTART (required by ICS standard)
-			let { startICS, endICS } = this.getICSDateFormat(task);
+			let { startICS, endICS } = this.getICSDateFormat(task, true, options);
 
 			// If no start date, use task creation date or current date as fallback
 			if (!startICS) {
@@ -567,7 +580,7 @@ export class CalendarExportService {
 	/**
 	 * Download ICS file for all tasks
 	 */
-	static downloadAllTasksICSFile(tasks: TaskInfo[], translate?: TranslateFn): void {
+	static downloadAllTasksICSFile(tasks: TaskInfo[], translate?: TranslateFn, options?: ICSExportOptions): void {
 		try {
 			if (!tasks || tasks.length === 0) {
 				new Notice(
@@ -578,7 +591,7 @@ export class CalendarExportService {
 				return;
 			}
 
-			const icsContent = this.generateMultipleTasksICSContent(tasks);
+			const icsContent = this.generateMultipleTasksICSContent(tasks, options);
 			const blob = new Blob([icsContent], { type: "text/calendar" });
 			const url = URL.createObjectURL(blob);
 
@@ -615,9 +628,9 @@ export class CalendarExportService {
 	/**
 	 * Download ICS file for a task
 	 */
-	static downloadICSFile(task: TaskInfo, translate?: TranslateFn): void {
+	static downloadICSFile(task: TaskInfo, translate?: TranslateFn, options?: ICSExportOptions): void {
 		try {
-			const icsContent = this.generateICSContent(task);
+			const icsContent = this.generateICSContent(task, options);
 			const blob = new Blob([icsContent], { type: "text/calendar" });
 			const url = URL.createObjectURL(blob);
 

src/settings/defaults.ts

@@ -189,6 +189,7 @@ export const DEFAULT_ICS_INTEGRATION_SETTINGS: ICSIntegrationSettings = {
 	enableAutoExport: false,
 	autoExportPath: "tasknotes-calendar.ics",
 	autoExportInterval: 60, // 60 minutes by default
+	useDurationForExport: false, // Preserve existing behavior: use due date as DTEND
 	// Task creation defaults
 	useICSEndAsDue: false, // Preserve existing behavior: don't set due date from ICS events
 };

src/settings/tabs/integrationsTab.ts

@@ -1029,6 +1029,18 @@ export function renderIntegrationsTab(
 					})
 				);
 
+				group.addSetting((setting) =>
+					configureToggleSetting(setting, {
+						name: translate("settings.integrations.autoExport.useDuration.name"),
+						desc: translate("settings.integrations.autoExport.useDuration.description"),
+						getValue: () => plugin.settings.icsIntegration.useDurationForExport ?? false,
+						setValue: async (value: boolean) => {
+							plugin.settings.icsIntegration.useDurationForExport = value;
+							save();
+						},
+					})
+				);
+
 				// Manual export trigger button
 				group.addSetting((setting) =>
 					configureButtonSetting(setting, {

src/types/settings.ts

@@ -280,6 +280,7 @@ export interface ICSIntegrationSettings {
 	enableAutoExport: boolean; // Whether to automatically export tasks to ICS file
 	autoExportPath: string; // Path where the ICS file should be saved
 	autoExportInterval: number; // Export interval in minutes (default: 60)
+	useDurationForExport: boolean; // Whether to use timeEstimate (duration) instead of due date for DTEND
 	// Task creation from ICS events
 	useICSEndAsDue: boolean; // Whether to use ICS event end time as task due date
 }