The Events Calendar: Remove the month, day, and datetime separator from an event's start time display.

functions.php

<?php
/**
 * The Events Calendar: Remove the month, day, and datetime separator from an event's start time display.
 *
 * Example:
 *   Before: <span class="tribe-event-date-start">January 31 @ 10:30 pm</span> - <span ...
 *   After: <span class="tribe-event-date-start">10:30 pm</span> - <span ...
 * DOES NOT APPLY WHEN USING WordPress 5's BLOCK EDITOR. For block editor, just use this CSS:
 *   .tribe-events-schedule__datetime > .tribe-events-schedule__date--start,
 *   .tribe-events-schedule__datetime > .tribe-events-schedule__separator--date {
 *     display: none;
 *   }
 *
 * @link https://gist.github.com/cliffordp/94012b1623319b20c93b04aa050ce917 This snippet.
 *
 * @see tribe_events_event_schedule_details()
 *
 * @param string $inner
 * @param int $event_id
 *
 * @return string
 */
function cliff_tribe_remove_day_from_start( $inner, $event_id ) {
	$start = '<span class="tribe-event-date-start">';

	// If doesn't start as expected, bail
	if ( 0 !== strpos( $inner, $start ) ) {
		return $inner;
	}

	$datetime_separator = tribe_get_option( 'dateTimeSeparator', ' @ ' );

	$remove_this = tribe_get_start_date( $event_id, false, '' ) . $datetime_separator;

	$inner = str_replace( $remove_this, '', $inner );

	return $inner;
}

add_filter( 'tribe_events_event_schedule_details_inner', 'cliff_tribe_remove_day_from_start', 10, 2 );