Override Mini-Calendar Widget -- output month name abbreviation instead of day name abbreviation -- e.g. change "Sat" to "Oct"

functions.php

<?php

// http://theeventscalendar.com/support/forums/topic/events-list-widget-not-showing-the-month-just-day-name-and-day-number/
//
// Mini-Calendar Widget: /wp-content/plugins/events-calendar-pro/src/views/pro/widgets/modules/single-event.php
// output month name abbreviation instead of day name abbreviation
// e.g. change "Sat" to "Oct"
add_filter( 'tribe-mini_helper_tribe_events_ajax_list_dayname', 'cliff_1011625_mini_cal_month_instead_of_day_of_week' );
function cliff_1011625_mini_cal_month_instead_of_day_of_week( $postDate ) {
  return date_i18n( 'M', strtotime( $postDate ) ); // changing from 'D' to 'M' -- could also use any other date format from http://php.net/manual/en/function.date.php
}