This snippet fixes the 'Month/Year' dropdown on Event Espresso -> Events when our site is set not to use a year i the date format.

tw_ee_fix_month_year_dropdown_with_no_year.php

<?php

add_filter('FHEE__Events_Admin_Page__get_events__where', 'tw_ee_fix_month_year_dropdown_with_no_year', 10, 2);
function tw_ee_fix_month_year_dropdown_with_no_year( $where, $req_data ) {
        // If month_range is empty, we have nothing to do here.
        if(empty($req_data['month_range'])) {
            return $where;
        }

        if (isset($req_data['month_range'])) {
            $pieces = explode(' ', $req_data['month_range'], 3);
            // simulate the FIRST day of the month, that fixes issues for months like February
            // where PHP doesn't know what to assume for date.
            // @see https://events.codebasehq.com/projects/event-espresso/tickets/10437
            $month_r = ! empty($pieces[0]) ? date('m', \EEH_DTT_Helper::first_of_month_timestamp($pieces[0])) : '';
            $year_r = ! empty($pieces[1]) ? $pieces[1] : '';
        }

        $DateTime = new DateTime(
            $year_r . '-' . $month_r . '-01 00:00:00',
            new DateTimeZone('UTC')
        );
        $start = $DateTime->getTimestamp();
        // set the datetime to be the end of the month
        $DateTime->setDate(
            $year_r,
            $month_r,
            $DateTime->format('t')
        )->setTime(23, 59, 59);
        $end = $DateTime->getTimestamp();
        $where['Datetime.DTT_EVT_start'] = array('BETWEEN', array($start, $end));

        return $where;
}