Save some queries with the class Tribe_Events_Month_Template

<?php
/**
 * @for Calendar Template
 * This file contains the hook logic required to create an effective calendar month view.
 *
 * @package TribeEventsCalendar
 * @since  2.1
 * @author Modern Tribe Inc.
 *
 */

if ( !defined('ABSPATH') ) { die('-1'); }

if( !class_exists('Tribe_Events_Month_Template')){
    /**
     * Grid view template class
     */
    class Tribe_Events_Month_Template extends Tribe_Template_Factory {
        private static $has_posts = array();

        /**
         * @param string $date
         * @return WP_Query
         */
        private function get_daily_events( $date ) {
            global $wp_query;
            $tribe_ecp = TribeEvents::instance();

            $post_status = is_user_logged_in() ? array( 'publish', 'private' ) : 'publish';

            //// Changes start here
            $args = wp_parse_args( array(
                // setup our own custom hide upcoming
                'post__not_in' => self::$hide_upcoming_ids,
                'hide_upcoming' => false,
                'posts_per_page' => self::$posts_per_page_limit,
                'orderby' => 'menu_order',
                'order' => 'ASC',
                'post_status' => $post_status,
                'eventDisplay' => 'custom',
                'no_found_rows' => true
            ), self::$args );

            // If we know this date does not have events, build a "empty WP_Query" that can be cached for all other "empty days"
            if ( isset($this->has_posts[$date]) ) {
                $args = array_merge( $args, array(
                    'eventDate' => $date,
                    'start_date' => tribe_event_beginning_of_day( $date ),
                    'end_date' => tribe_event_end_of_day( $date ),
                ) );
                if ( is_tax( $tribe_ecp->get_event_taxonomy() ) ) {
                    $cat = get_term_by( 'slug', get_query_var( 'term' ), $tribe_ecp->get_event_taxonomy() );
                    $args['eventCat'] = (int) $cat->term_id;
                }
            }
            else
                $args['p'] = 965060879876;  // Now pray that this one does not exist
            //// Changes stop here

            $cache = new TribeEventsCache();
            $cache_key = 'daily_events_'.serialize($args);
            $found = $cache->get($cache_key, 'save_post');
            if ( $found && is_a($found, 'WP_Query') ) {
                // return $found;
            }

            $result = TribeEventsQuery::getEvents( $args, true );
            $cache->set($cache_key, $result, self::$cache_expiration, 'save_post');
            return $result;
        }

        /**
         * Sets up an array of $days based on the current query, that can be used in the calendar loop
         *
         * @return void
         * @since 3.0
         **/
        public function setup_view() {

            $tribe_ecp = TribeEvents::instance();
            $tribe_ecp->date = isset( self::$args['eventDate'] ) ? self::$args['eventDate'] : tribe_get_month_view_date();

            // get all upcoming ids to hide so we're not querying 31 times
            self::$hide_upcoming_ids = TribeEventsQuery::getHideFromUpcomingEvents();

            list( $year, $month ) = explode( '-', $tribe_ecp->date );

            $first_date_of_month = mktime( 12, 0, 0, $month, 1, $year ); // 1st day of month as unix stamp

            //// Changes start here
            // The idea is to fetch all events at once. This way we can tell which days have no events and use the cache.
            $first_day_of_month  = date('Y-m-01', $first_date_of_month);
            $last_day_of_month   = date('Y-m-t', $first_date_of_month);

            $post_status = is_user_logged_in() ? array( 'publish', 'private' ) : 'publish';
            $args = array(
                'post_status'   => $post_status,
                'posts_per_page'=> -1,
                'eventDate'     => $first_day_of_month,
                'start_date'    => tribe_event_beginning_of_day( $first_day_of_month ),
                'end_date'      => tribe_event_end_of_day( $last_day_of_month ),
                'post__not_in'  => self::$hide_upcoming_ids,
                'eventDisplay'  => 'custom',
                'hide_upcoming' => false,
                'no_found_rows' => true,
                'orderby'       => 'menu_order',
            );

            if ( is_tax( $tribe_ecp->get_event_taxonomy() ) ) {
                $cat = get_term_by( 'slug', get_query_var( 'term' ), $tribe_ecp->get_event_taxonomy() );
                $args['tax_query'] = array(
                    array(
                        'taxonomy'  => TribeEvents::TAXONOMY,
                        'field'     => 'id',
                        'terms'     => (int) $cat->term_id
                    )
                );
            }

            // Get all events of this month
            $result = TribeEventsQuery::getEvents( $args, true );

            // Store the info
            if ( count($result->posts) ) {
                foreach ( $result->posts as $r ) {
                    $this->has_posts[reset(explode(' ', $r->EventStartDate))] = 1;
                }
            }
            unset($result);
            //// Changes stop here

            $startOfWeek = get_option( 'start_of_week', 0 );

            self::$event_daily_counts = self::get_daily_counts($first_date_of_month);

            if ( empty(self::$tribe_bar_args) ) {
                foreach ( $_REQUEST as $key => $value ) {
                    if ( $value && strpos($key, 'tribe-bar-') === 0 && $key != 'tribe-bar-date' ) {
                        self::$tribe_bar_args[$key] = $value;
                    }
                }
            }

            // Var'ng up days, months and years
            self::$today = date_i18n( 'd' );
            self::$current_month = date_i18n( 'm' );
            self::$current_year = date_i18n( 'Y' );

            // single dimensional array of days for the month
            $days = array();

            // setup counters
            $rawOffset = date( 'w', $first_date_of_month ) - $startOfWeek;
            $prev_month_offset = (int) ( ( $rawOffset < 0 ) ? $rawOffset + 7 : $rawOffset ); // month begins on day x
            $days_in_month = (int) date( 't', intval( $first_date_of_month ) );
            $days_in_calendar =  $days_in_month + $prev_month_offset;
            while ($days_in_calendar % 7 > 0) {
                $days_in_calendar++;
            }
            $week = 0;
            $cur_calendar_day = 0;

            // fill month with required days for previous month
            if ( $prev_month_offset > 0 )
                $days = array_fill( 0, $prev_month_offset, array( 'date' => 'previous' ) );

            // get $cur_calendar_day up to speed
            $cur_calendar_day += $prev_month_offset;

            // add days for this month
            for ($i = 0; $i < $days_in_month; $i++) {
                $day = $i + 1;
                $date = date( 'Y-m-d', strtotime("$year-$month-$day"));

                $total_events = ! empty( self::$event_daily_counts[$date] ) ? self::$event_daily_counts[$date] : 0;

                $days[] = array(
                    'daynum'       => $day,
                    'date'         => $date,
                    'events'       => self::get_daily_events( $date ),
                    'total_events' => $total_events,
                    'view_more'    => self::view_more_link( $date, self::$tribe_bar_args ),
                );
            }

            // get $cur_calendar_day up to speed
            $cur_calendar_day += $days_in_month;

            // check if $cur_calendar_day is less than $days_in_calendar, if so, add days for next month
            if ($cur_calendar_day < $days_in_calendar) {
                $days = array_merge($days, array_fill($cur_calendar_day, $days_in_calendar - $cur_calendar_day, array('date' => 'next')));
            }

            // store set of found days for use in calendar loop functions
            self::$calendar_days = $days;
        }

    } // class Tribe_Events_Month_Template
}