diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index fd5d9e62ba63e..200e2e75612c6 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -192,6 +192,7 @@
     'OCP\\Calendar\\BackendTemporarilyUnavailableException' => $baseDir . '/lib/public/Calendar/BackendTemporarilyUnavailableException.php',
     'OCP\\Calendar\\Exceptions\\CalendarException' => $baseDir . '/lib/public/Calendar/Exceptions/CalendarException.php',
     'OCP\\Calendar\\ICalendar' => $baseDir . '/lib/public/Calendar/ICalendar.php',
+    'OCP\\Calendar\\ICalendarEventBuilder' => $baseDir . '/lib/public/Calendar/ICalendarEventBuilder.php',
     'OCP\\Calendar\\ICalendarIsShared' => $baseDir . '/lib/public/Calendar/ICalendarIsShared.php',
     'OCP\\Calendar\\ICalendarIsWritable' => $baseDir . '/lib/public/Calendar/ICalendarIsWritable.php',
     'OCP\\Calendar\\ICalendarProvider' => $baseDir . '/lib/public/Calendar/ICalendarProvider.php',
@@ -1116,6 +1117,7 @@
     'OC\\Broadcast\\Events\\BroadcastEvent' => $baseDir . '/lib/private/Broadcast/Events/BroadcastEvent.php',
     'OC\\Cache\\CappedMemoryCache' => $baseDir . '/lib/private/Cache/CappedMemoryCache.php',
     'OC\\Cache\\File' => $baseDir . '/lib/private/Cache/File.php',
+    'OC\\Calendar\\CalendarEventBuilder' => $baseDir . '/lib/private/Calendar/CalendarEventBuilder.php',
     'OC\\Calendar\\CalendarQuery' => $baseDir . '/lib/private/Calendar/CalendarQuery.php',
     'OC\\Calendar\\Manager' => $baseDir . '/lib/private/Calendar/Manager.php',
     'OC\\Calendar\\Resource\\Manager' => $baseDir . '/lib/private/Calendar/Resource/Manager.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index d9af7846bd882..a7a8e5a800f24 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -241,6 +241,7 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OCP\\Calendar\\BackendTemporarilyUnavailableException' => __DIR__ . '/../../..' . '/lib/public/Calendar/BackendTemporarilyUnavailableException.php',
         'OCP\\Calendar\\Exceptions\\CalendarException' => __DIR__ . '/../../..' . '/lib/public/Calendar/Exceptions/CalendarException.php',
         'OCP\\Calendar\\ICalendar' => __DIR__ . '/../../..' . '/lib/public/Calendar/ICalendar.php',
+        'OCP\\Calendar\\ICalendarEventBuilder' => __DIR__ . '/../../..' . '/lib/public/Calendar/ICalendarEventBuilder.php',
         'OCP\\Calendar\\ICalendarIsShared' => __DIR__ . '/../../..' . '/lib/public/Calendar/ICalendarIsShared.php',
         'OCP\\Calendar\\ICalendarIsWritable' => __DIR__ . '/../../..' . '/lib/public/Calendar/ICalendarIsWritable.php',
         'OCP\\Calendar\\ICalendarProvider' => __DIR__ . '/../../..' . '/lib/public/Calendar/ICalendarProvider.php',
@@ -1165,6 +1166,7 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\Broadcast\\Events\\BroadcastEvent' => __DIR__ . '/../../..' . '/lib/private/Broadcast/Events/BroadcastEvent.php',
         'OC\\Cache\\CappedMemoryCache' => __DIR__ . '/../../..' . '/lib/private/Cache/CappedMemoryCache.php',
         'OC\\Cache\\File' => __DIR__ . '/../../..' . '/lib/private/Cache/File.php',
+        'OC\\Calendar\\CalendarEventBuilder' => __DIR__ . '/../../..' . '/lib/private/Calendar/CalendarEventBuilder.php',
         'OC\\Calendar\\CalendarQuery' => __DIR__ . '/../../..' . '/lib/private/Calendar/CalendarQuery.php',
         'OC\\Calendar\\Manager' => __DIR__ . '/../../..' . '/lib/private/Calendar/Manager.php',
         'OC\\Calendar\\Resource\\Manager' => __DIR__ . '/../../..' . '/lib/private/Calendar/Resource/Manager.php',
diff --git a/lib/private/Calendar/CalendarEventBuilder.php b/lib/private/Calendar/CalendarEventBuilder.php
new file mode 100644
index 0000000000000..9198d383ef940
--- /dev/null
+++ b/lib/private/Calendar/CalendarEventBuilder.php
@@ -0,0 +1,132 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OC\Calendar;
+
+use DateTimeInterface;
+use InvalidArgumentException;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\Calendar\ICalendarEventBuilder;
+use OCP\Calendar\ICreateFromString;
+use Sabre\VObject\Component\VCalendar;
+use Sabre\VObject\Component\VEvent;
+
+class CalendarEventBuilder implements ICalendarEventBuilder {
+	private ?DateTimeInterface $startDate = null;
+	private ?DateTimeInterface $endDate = null;
+	private ?string $summary = null;
+	private ?string $description = null;
+	private ?string $location = null;
+	private ?array $organizer = null;
+	private array $attendees = [];
+
+	public function __construct(
+		private readonly string $uid,
+		private readonly ITimeFactory $timeFactory,
+	) {
+	}
+
+	public function setStartDate(DateTimeInterface $start): ICalendarEventBuilder {
+		$this->startDate = $start;
+		return $this;
+	}
+
+	public function setEndDate(DateTimeInterface $end): ICalendarEventBuilder {
+		$this->endDate = $end;
+		return $this;
+	}
+
+	public function setSummary(string $summary): ICalendarEventBuilder {
+		$this->summary = $summary;
+		return $this;
+	}
+
+	public function setDescription(string $description): ICalendarEventBuilder {
+		$this->description = $description;
+		return $this;
+	}
+
+	public function setLocation(string $location): ICalendarEventBuilder {
+		$this->location = $location;
+		return $this;
+	}
+
+	public function setOrganizer(string $email, ?string $commonName = null): ICalendarEventBuilder {
+		$this->organizer = [$email, $commonName];
+		return $this;
+	}
+
+	public function addAttendee(string $email, ?string $commonName = null): ICalendarEventBuilder {
+		$this->attendees[] = [$email, $commonName];
+		return $this;
+	}
+
+	public function toIcs(): string {
+		if ($this->startDate === null) {
+			throw new InvalidArgumentException('Event is missing a start date');
+		}
+
+		if ($this->endDate === null) {
+			throw new InvalidArgumentException('Event is missing an end date');
+		}
+
+		if ($this->summary === null) {
+			throw new InvalidArgumentException('Event is missing a summary');
+		}
+
+		if ($this->organizer === null && $this->attendees !== []) {
+			throw new InvalidArgumentException('Event has attendees but is missing an organizer');
+		}
+
+		$vcalendar = new VCalendar();
+		$props = [
+			'UID' => $this->uid,
+			'DTSTAMP' => $this->timeFactory->now(),
+			'SUMMARY' => $this->summary,
+			'DTSTART' => $this->startDate,
+			'DTEND' => $this->endDate,
+		];
+		if ($this->description !== null) {
+			$props['DESCRIPTION'] = $this->description;
+		}
+		if ($this->location !== null) {
+			$props['LOCATION'] = $this->location;
+		}
+		/** @var VEvent $vevent */
+		$vevent = $vcalendar->add('VEVENT', $props);
+		if ($this->organizer !== null) {
+			self::addAttendeeToVEvent($vevent, 'ORGANIZER', $this->organizer);
+		}
+		foreach ($this->attendees as $attendee) {
+			self::addAttendeeToVEvent($vevent, 'ATTENDEE', $attendee);
+		}
+		return $vcalendar->serialize();
+	}
+
+	public function createInCalendar(ICreateFromString $calendar): string {
+		$fileName = $this->uid . '.ics';
+		$calendar->createFromString($fileName, $this->toIcs());
+		return $fileName;
+	}
+
+	/**
+	 * @param array{0: string, 1: ?string} $tuple A tuple of [$email, $commonName] where $commonName may be null.
+	 */
+	private static function addAttendeeToVEvent(VEvent $vevent, string $name, array $tuple): void {
+		[$email, $cn] = $tuple;
+		if (!str_starts_with($email, 'mailto:')) {
+			$email = "mailto:$email";
+		}
+		$params = [];
+		if ($cn !== null) {
+			$params['CN'] = $cn;
+		}
+		$vevent->add($name, $email, $params);
+	}
+}
diff --git a/lib/private/Calendar/Manager.php b/lib/private/Calendar/Manager.php
index ba2124a5c239a..3469193a364d1 100644
--- a/lib/private/Calendar/Manager.php
+++ b/lib/private/Calendar/Manager.php
@@ -12,6 +12,7 @@
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\Calendar\Exceptions\CalendarException;
 use OCP\Calendar\ICalendar;
+use OCP\Calendar\ICalendarEventBuilder;
 use OCP\Calendar\ICalendarIsShared;
 use OCP\Calendar\ICalendarIsWritable;
 use OCP\Calendar\ICalendarProvider;
@@ -19,6 +20,7 @@
 use OCP\Calendar\ICreateFromString;
 use OCP\Calendar\IHandleImipMessage;
 use OCP\Calendar\IManager;
+use OCP\Security\ISecureRandom;
 use Psr\Container\ContainerInterface;
 use Psr\Log\LoggerInterface;
 use Sabre\VObject\Component\VCalendar;
@@ -45,6 +47,7 @@ public function __construct(
 		private ContainerInterface $container,
 		private LoggerInterface $logger,
 		private ITimeFactory $timeFactory,
+		private ISecureRandom $random,
 	) {
 	}
 
@@ -216,21 +219,21 @@ public function handleIMipRequest(
 		string $recipient,
 		string $calendarData,
 	): bool {
-		
+
 		$userCalendars = $this->getCalendarsForPrincipal($principalUri);
 		if (empty($userCalendars)) {
 			$this->logger->warning('iMip message could not be processed because user has no calendars');
 			return false;
 		}
-		
+
 		/** @var VCalendar $vObject|null */
 		$calendarObject = Reader::read($calendarData);
-		
+
 		if (!isset($calendarObject->METHOD) || $calendarObject->METHOD->getValue() !== 'REQUEST') {
 			$this->logger->warning('iMip message contains an incorrect or invalid method');
 			return false;
 		}
-		
+
 		if (!isset($calendarObject->VEVENT)) {
 			$this->logger->warning('iMip message contains no event');
 			return false;
@@ -242,12 +245,12 @@ public function handleIMipRequest(
 			$this->logger->warning('iMip message event dose not contains a UID');
 			return false;
 		}
-		
+
 		if (!isset($eventObject->ATTENDEE)) {
 			$this->logger->warning('iMip message event dose not contains any attendees');
 			return false;
 		}
-		
+
 		foreach ($eventObject->ATTENDEE as $entry) {
 			$address = trim(str_replace('mailto:', '', $entry->getValue()));
 			if ($address === $recipient) {
@@ -259,17 +262,17 @@ public function handleIMipRequest(
 			$this->logger->warning('iMip message event does not contain a attendee that matches the recipient');
 			return false;
 		}
-		
+
 		foreach ($userCalendars as $calendar) {
-			
+
 			if (!$calendar instanceof ICalendarIsWritable && !$calendar instanceof ICalendarIsShared) {
 				continue;
 			}
-			
+
 			if ($calendar->isDeleted() || !$calendar->isWritable() || $calendar->isShared()) {
 				continue;
 			}
-			
+
 			if (!empty($calendar->search($recipient, ['ATTENDEE'], ['uid' => $eventObject->UID->getValue()]))) {
 				try {
 					if ($calendar instanceof IHandleImipMessage) {
@@ -282,7 +285,7 @@ public function handleIMipRequest(
 				}
 			}
 		}
-		
+
 		$this->logger->warning('iMip message event could not be processed because the no corresponding event was found in any calendar');
 		return false;
 	}
@@ -464,4 +467,9 @@ public function handleIMipCancel(
 			return false;
 		}
 	}
+
+	public function createEventBuilder(): ICalendarEventBuilder {
+		$uid = $this->random->generate(32, ISecureRandom::CHAR_ALPHANUMERIC);
+		return new CalendarEventBuilder($uid, $this->timeFactory);
+	}
 }
diff --git a/lib/public/Calendar/ICalendarEventBuilder.php b/lib/public/Calendar/ICalendarEventBuilder.php
new file mode 100644
index 0000000000000..8afc817a61ec4
--- /dev/null
+++ b/lib/public/Calendar/ICalendarEventBuilder.php
@@ -0,0 +1,110 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCP\Calendar;
+
+use DateTimeInterface;
+use InvalidArgumentException;
+use OCP\Calendar\Exceptions\CalendarException;
+
+/**
+ * The calendar event builder can be used to conveniently build a calendar event and then serialize
+ * it to a ICS string. The ICS string can be submitted to calendar instances implementing the
+ * {@see \OCP\Calendar\ICreateFromString} interface.
+ *
+ * Also note this class can not be injected directly with dependency injection.
+ * Instead, inject {@see \OCP\Calendar\IManager} and use
+ * {@see \OCP\Calendar\IManager::createEventBuilder()} afterwards.
+ *
+ * All setters return self to allow chaining method calls.
+ *
+ * @since 31.0.0
+ */
+interface ICalendarEventBuilder {
+	/**
+	 * Set the start date, time and time zone.
+	 * This property is required!
+	 *
+	 * @since 31.0.0
+	 */
+	public function setStartDate(DateTimeInterface $start): self;
+
+	/**
+	 * Set the end date, time and time zone.
+	 * This property is required!
+	 *
+	 * @since 31.0.0
+	 */
+	public function setEndDate(DateTimeInterface $end): self;
+
+	/**
+	 * Set the event summary or title.
+	 * This property is required!
+	 *
+	 * @since 31.0.0
+	 */
+	public function setSummary(string $summary): self;
+
+	/**
+	 * Set the event description.
+	 *
+	 * @since 31.0.0
+	 */
+	public function setDescription(string $description): self;
+
+	/**
+	 * Set the event location. It can either be a physical address or a URL.
+	 *
+	 * @since 31.0.0
+	 */
+	public function setLocation(string $location): self;
+
+	/**
+	 * Set the event organizer.
+	 * This property is required if attendees are added!
+	 *
+	 * The "mailto:" prefix is optional and will be added automatically if it is missing.
+	 *
+	 * @since 31.0.0
+	 */
+	public function setOrganizer(string $email, ?string $commonName = null): self;
+
+	/**
+	 * Add a new attendee to the event.
+	 * Adding at least one attendee requires also setting the organizer!
+	 *
+	 * The "mailto:" prefix is optional and will be added automatically if it is missing.
+	 *
+	 * @since 31.0.0
+	 */
+	public function addAttendee(string $email, ?string $commonName = null): self;
+
+	/**
+	 * Serialize the built event to an ICS string if all required properties set.
+	 *
+	 * @since 31.0.0
+	 *
+	 * @return string The serialized ICS string
+	 *
+	 * @throws InvalidArgumentException If required properties were not set
+	 */
+	public function toIcs(): string;
+
+	/**
+	 * Create the event in the given calendar.
+	 *
+	 * @since 31.0.0
+	 *
+	 * @return string The filename of the created event
+	 *
+	 * @throws InvalidArgumentException If required properties were not set
+	 * @throws CalendarException If writing the event to the calendar fails
+	 */
+	public function createInCalendar(ICreateFromString $calendar): string;
+}
diff --git a/lib/public/Calendar/IManager.php b/lib/public/Calendar/IManager.php
index bb3808f133c8d..8056d57d859a7 100644
--- a/lib/public/Calendar/IManager.php
+++ b/lib/public/Calendar/IManager.php
@@ -157,4 +157,12 @@ public function handleIMipReply(string $principalUri, string $sender, string $re
 	 * @since 25.0.0
 	 */
 	public function handleIMipCancel(string $principalUri, string $sender, ?string $replyTo, string $recipient, string $calendarData): bool;
+
+	/**
+	 * Create a new event builder instance. Please have a look at its documentation and the
+	 * \OCP\Calendar\ICreateFromString interface on how to use it.
+	 *
+	 * @since 31.0.0
+	 */
+	public function createEventBuilder(): ICalendarEventBuilder;
 }
diff --git a/tests/data/ics/event-builder-complete.ics b/tests/data/ics/event-builder-complete.ics
new file mode 100644
index 0000000000000..d96a313735637
--- /dev/null
+++ b/tests/data/ics/event-builder-complete.ics
@@ -0,0 +1,16 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Sabre//Sabre VObject 4.5.6//EN
+CALSCALE:GREGORIAN
+BEGIN:VEVENT
+UID:event-uid-123
+DTSTAMP:20250105T000000Z
+SUMMARY:My event
+DTSTART:20250105T170958Z
+DTEND:20250105T171958Z
+DESCRIPTION:Foo bar baz
+ORGANIZER:mailto:organizer@domain.tld
+ATTENDEE:mailto:attendee1@domain.tld
+ATTENDEE:mailto:attendee2@domain.tld
+END:VEVENT
+END:VCALENDAR
diff --git a/tests/data/ics/event-builder-complete.ics.license b/tests/data/ics/event-builder-complete.ics.license
new file mode 100644
index 0000000000000..f7f52efa96fde
--- /dev/null
+++ b/tests/data/ics/event-builder-complete.ics.license
@@ -0,0 +1,2 @@
+SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+SPDX-License-Identifier: AGPL-3.0-or-later
diff --git a/tests/data/ics/event-builder-without-attendees.ics b/tests/data/ics/event-builder-without-attendees.ics
new file mode 100644
index 0000000000000..95c4c44fa1fd1
--- /dev/null
+++ b/tests/data/ics/event-builder-without-attendees.ics
@@ -0,0 +1,13 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Sabre//Sabre VObject 4.5.6//EN
+CALSCALE:GREGORIAN
+BEGIN:VEVENT
+UID:event-uid-123
+DTSTAMP:20250105T000000Z
+SUMMARY:My event
+DTSTART:20250105T170958Z
+DTEND:20250105T171958Z
+DESCRIPTION:Foo bar baz
+END:VEVENT
+END:VCALENDAR
diff --git a/tests/data/ics/event-builder-without-attendees.ics.license b/tests/data/ics/event-builder-without-attendees.ics.license
new file mode 100644
index 0000000000000..f7f52efa96fde
--- /dev/null
+++ b/tests/data/ics/event-builder-without-attendees.ics.license
@@ -0,0 +1,2 @@
+SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+SPDX-License-Identifier: AGPL-3.0-or-later
diff --git a/tests/lib/Calendar/CalendarEventBuilderTest.php b/tests/lib/Calendar/CalendarEventBuilderTest.php
new file mode 100644
index 0000000000000..48684d560939b
--- /dev/null
+++ b/tests/lib/Calendar/CalendarEventBuilderTest.php
@@ -0,0 +1,146 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\Calendar;
+
+use DateTimeImmutable;
+use InvalidArgumentException;
+use OC\Calendar\CalendarEventBuilder;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\Calendar\ICreateFromString;
+use PHPUnit\Framework\MockObject\MockObject;
+use Test\TestCase;
+
+class CalendarEventBuilderTest extends TestCase {
+	private CalendarEventBuilder $calendarEventBuilder;
+	private ITimeFactory&MockObject $timeFactory;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->timeFactory = $this->createMock(ITimeFactory::class);
+		$this->timeFactory->method('now')
+			->willReturn(new DateTimeImmutable('20250105T000000Z'));
+
+		$this->calendarEventBuilder = new CalendarEventBuilder(
+			'event-uid-123',
+			$this->timeFactory,
+		);
+	}
+
+	public function testToIcs(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->setOrganizer('mailto:organizer@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee2@domain.tld');
+
+		$expected = file_get_contents(\OC::$SERVERROOT . '/tests/data/ics/event-builder-complete.ics');
+		$actual = $this->calendarEventBuilder->toIcs();
+		$this->assertEquals($expected, $actual);
+	}
+
+	public function testToIcsWithoutOrganizerAndAttendees(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+
+		$expected = file_get_contents(\OC::$SERVERROOT . '/tests/data/ics/event-builder-without-attendees.ics');
+		$actual = $this->calendarEventBuilder->toIcs();
+		$this->assertEquals($expected, $actual);
+	}
+
+	public function testToIcsWithoutMailtoPrefix(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->setOrganizer('organizer@domain.tld');
+		$this->calendarEventBuilder->addAttendee('attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('attendee2@domain.tld');
+
+		$expected = file_get_contents(\OC::$SERVERROOT . '/tests/data/ics/event-builder-complete.ics');
+		$actual = $this->calendarEventBuilder->toIcs();
+		$this->assertEquals($expected, $actual);
+	}
+
+	public function testCreateInCalendar(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->setOrganizer('organizer@domain.tld');
+		$this->calendarEventBuilder->addAttendee('attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee2@domain.tld');
+
+		$expectedIcs = file_get_contents(\OC::$SERVERROOT . '/tests/data/ics/event-builder-complete.ics');
+		$calendar = $this->createMock(ICreateFromString::class);
+		$calendar->expects(self::once())
+			->method('createFromString')
+			->with('event-uid-123.ics', $expectedIcs);
+
+		$actual = $this->calendarEventBuilder->createInCalendar($calendar);
+		$this->assertEquals('event-uid-123.ics', $actual);
+	}
+
+	public function testToIcsWithoutStartDate(): void {
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->setOrganizer('organizer@domain.tld');
+		$this->calendarEventBuilder->addAttendee('attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee2@domain.tld');
+
+		$this->expectException(InvalidArgumentException::class);
+		$this->expectExceptionMessageMatches('/start date/i');
+		$this->calendarEventBuilder->toIcs();
+	}
+
+	public function testToIcsWithoutEndDate(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->setOrganizer('organizer@domain.tld');
+		$this->calendarEventBuilder->addAttendee('attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee2@domain.tld');
+
+		$this->expectException(InvalidArgumentException::class);
+		$this->expectExceptionMessageMatches('/end date/i');
+		$this->calendarEventBuilder->toIcs();
+	}
+
+	public function testToIcsWithoutSummary(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->setOrganizer('organizer@domain.tld');
+		$this->calendarEventBuilder->addAttendee('attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee2@domain.tld');
+
+		$this->expectException(InvalidArgumentException::class);
+		$this->expectExceptionMessageMatches('/summary/i');
+		$this->calendarEventBuilder->toIcs();
+	}
+
+	public function testToIcsWithoutOrganizerWithAttendees(): void {
+		$this->calendarEventBuilder->setStartDate(new DateTimeImmutable('2025-01-05T17:09:58Z'));
+		$this->calendarEventBuilder->setEndDate(new DateTimeImmutable('2025-01-05T17:19:58Z'));
+		$this->calendarEventBuilder->setSummary('My event');
+		$this->calendarEventBuilder->setDescription('Foo bar baz');
+		$this->calendarEventBuilder->addAttendee('attendee1@domain.tld');
+		$this->calendarEventBuilder->addAttendee('mailto:attendee2@domain.tld');
+
+		$this->expectException(InvalidArgumentException::class);
+		$this->expectExceptionMessageMatches('/organizer/i');
+		$this->calendarEventBuilder->toIcs();
+	}
+}
diff --git a/tests/lib/Calendar/ManagerTest.php b/tests/lib/Calendar/ManagerTest.php
index f0ca278f352ff..a7aeed98046c0 100644
--- a/tests/lib/Calendar/ManagerTest.php
+++ b/tests/lib/Calendar/ManagerTest.php
@@ -14,6 +14,7 @@
 use OCP\Calendar\ICalendarIsWritable;
 use OCP\Calendar\ICreateFromString;
 use OCP\Calendar\IHandleImipMessage;
+use OCP\Security\ISecureRandom;
 use PHPUnit\Framework\MockObject\MockObject;
 use Psr\Container\ContainerInterface;
 use Psr\Log\LoggerInterface;
@@ -44,6 +45,9 @@ class ManagerTest extends TestCase {
 	/** @var ITimeFactory&MockObject */
 	private $time;
 
+	/** @var ISecureRandom&MockObject */
+	private ISecureRandom $secureRandom;
+
 	private VCalendar $vCalendar1a;
 
 	protected function setUp(): void {
@@ -53,12 +57,14 @@ protected function setUp(): void {
 		$this->container = $this->createMock(ContainerInterface::class);
 		$this->logger = $this->createMock(LoggerInterface::class);
 		$this->time = $this->createMock(ITimeFactory::class);
+		$this->secureRandom = $this->createMock(ISecureRandom::class);
 
 		$this->manager = new Manager(
 			$this->coordinator,
 			$this->container,
 			$this->logger,
 			$this->time,
+			$this->secureRandom,
 		);
 
 		// construct calendar with a 1 hour event and same start/end time zones
@@ -260,7 +266,8 @@ public function testHandleImipRequestWithNoCalendars(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -291,7 +298,8 @@ public function testHandleImipRequestWithNoMethod(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -321,7 +329,8 @@ public function testHandleImipRequestWithInvalidMethod(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -352,7 +361,8 @@ public function testHandleImipRequestWithNoEvent(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -384,7 +394,8 @@ public function testHandleImipRequestWithNoUid(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -416,7 +427,8 @@ public function testHandleImipRequestWithNoAttendee(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -448,7 +460,8 @@ public function testHandleImipRequestWithInvalidAttendee(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -491,7 +504,8 @@ public function testHandleImipRequestWithNoMatch(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -534,7 +548,8 @@ public function testHandleImipRequest(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->onlyMethods(['getCalendarsForPrincipal'])
 			->getMock();
@@ -612,7 +627,8 @@ public function testHandleImipReplyNoCalendars(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->setMethods([
 				'getCalendarsForPrincipal'
@@ -643,7 +659,8 @@ public function testHandleImipReplyEventNotFound(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->setMethods([
 				'getCalendarsForPrincipal'
@@ -680,7 +697,8 @@ public function testHandleImipReply(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->setMethods([
 				'getCalendarsForPrincipal'
@@ -767,7 +785,8 @@ public function testHandleImipCancelNoCalendars(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->setMethods([
 				'getCalendarsForPrincipal'
@@ -800,7 +819,8 @@ public function testHandleImipCancelOrganiserInReplyTo(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->setMethods([
 				'getCalendarsForPrincipal'
@@ -837,7 +857,8 @@ public function testHandleImipCancel(): void {
 				$this->coordinator,
 				$this->container,
 				$this->logger,
-				$this->time
+				$this->time,
+				$this->secureRandom,
 			])
 			->setMethods([
 				'getCalendarsForPrincipal'
@@ -866,7 +887,7 @@ public function testHandleImipCancel(): void {
 		$result = $manager->handleIMipCancel($principalUri, $sender, $replyTo, $recipient, $calendarData->serialize());
 		$this->assertTrue($result);
 	}
-	
+
 	private function getVCalendarReply(): Document {
 		$data = <<<EOF
 BEGIN:VCALENDAR