diff --git a/static/scripts/calendar.js b/static/scripts/calendar.js
index 8e1d5813b3..41f28b801c 100644
--- a/static/scripts/calendar.js
+++ b/static/scripts/calendar.js
@@ -49,7 +49,8 @@ const getCalendarLanguage = (langAttribute) => {
 	}
 };
 
-// Add data-testid attributes to navigation buttons in calendar page
+// Add data-testid attributes to navigation buttons in calendar page as the calendar module
+// that is used (https://fullcalendar.io) does not support configuration of data-testids for buttons in used version
 const addDatatestidsToCalendarNavigation = () => {
 	const buttonData = [
 		{ selector: '.fc-right .fc-prev-button', testId: 'right-prev-button' },
@@ -63,7 +64,7 @@ const addDatatestidsToCalendarNavigation = () => {
 	buttonData.forEach(({ selector, testId }) => {
 		const button = document.querySelector(selector);
 		if (button) {
-			button.setAttribute('data-testid', testId);
+			button.dataset.testid = testId;
 		}
 	});
 };
@@ -138,12 +139,7 @@ $(document).ready(() => {
 	const getLangAttribute = () => document.querySelector('html').getAttribute('lang');
 
 	const calendar = new Calendar(getCalendarElement(), {
-		plugins: [
-			dayGridPlugin,
-			timeGridPlugin,
-			interactionPlugin,
-			momentTimezonePlugin,
-		],
+		plugins: [dayGridPlugin, timeGridPlugin, interactionPlugin, momentTimezonePlugin],
 		defaultView: getView() || 'dayGridMonth',
 		editable: false,
 		timeZone: getCalendarTimezone(),
@@ -167,12 +163,8 @@ $(document).ready(() => {
 				return false;
 			}
 			// personal event
-			const startDate = toMoment(event.start, calendar).format(
-				$t('format.dateTimeToPicker'),
-			);
-			const endDate = toMoment(event.end || event.start, calendar).format(
-				$t('format.dateTimeToPicker'),
-			);
+			const startDate = toMoment(event.start, calendar).format($t('format.dateTimeToPicker'));
+			const endDate = toMoment(event.end || event.start, calendar).format($t('format.dateTimeToPicker'));
 
 			const eventData = event.extendedProps || {};
 
@@ -191,8 +183,7 @@ $(document).ready(() => {
 				action: URI.getSingleEvent(eventData._id),
 			});
 
-			if (!eventData['x-sc-teamId']) {
-				// course or non-course event
+			if (!eventData['x-sc-teamId']) { // course or non-course event
 				transformCourseOrTeamEvent($editEventModal, eventData);
 				$editEventModal.find('.btn-delete').click(() => {
 					$.ajax({
@@ -207,8 +198,7 @@ $(document).ready(() => {
 				$editEventModal.appendTo('body').modal('show');
 			}
 
-			if (eventData['x-sc-teamId']) {
-				// team event
+			if (eventData['x-sc-teamId']) { // team event
 				const teamId = eventData['x-sc-teamId'];
 				window.location.assign(`/teams/${teamId}?activeTab=events`);
 			}
@@ -219,12 +209,8 @@ $(document).ready(() => {
 			const { date } = info;
 
 			// open create event modal
-			const startDate = toMoment(date, calendar).format(
-				$t('format.dateTimeToPicker'),
-			);
-			const endDate = toMoment(date, calendar)
-				.add(1, 'hour')
-				.format($t('format.dateTimeToPicker'));
+			const startDate = toMoment(date, calendar).format($t('format.dateTimeToPicker'));
+			const endDate = toMoment(date, calendar).add(1, 'hour').format($t('format.dateTimeToPicker'));
 
 			populateModalForm($createEventModal, {
 				title: $t('global.headline.addDate'),
@@ -344,4 +330,4 @@ $(document).ready(() => {
 			hideAreaByEvent(event);
 		}
 	});
-});
+});
\ No newline at end of file