Template file: /wp-content/plugins/the-events-calendar/src/views/v2/day/event/title.php

Override the above file with the following content, which inserts target="_blank" after the href attribute of the <a> element.

<h3 class="tribe-events-calendar-day__event-title tribe-common-h6 tribe-common-h4--min-medium">
	<a
		href="<?php echo esc_url( $event->permalink ); ?>"
		target="_blank"
		title="<?php echo esc_attr( $event->title ); ?>"
		rel="bookmark"
		class="tribe-events-calendar-day__event-title-link tribe-common-anchor-thin"
	>
		<?php
		// phpcs:ignore
		echo $event->title;
		?>
	</a>
</h3>
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