tribe_get_the_day_link bug. Line 16 in old.php was attributing $date_description to 'next day' as opposed to comparing that it was true. It also wasn't feeding date on line 19 a unix timestamp.

new.php

<?php
/** 
* Get the date for the day navigation link
*
* @param string $date_description
* @return string
* @since 3.1.1
* @throws OverflowException
*/
function tribe_get_the_day_link_date( $date_description ) { 
	if ( is_null($date_description) ) { 
	    return TribeEventsPro::instance()->todaySlug;
	}   
	if ( $date_description == 'previous day' ) { 
	    return tribe_get_previous_day_date(get_query_var('start_date'));
	}   
	if ( $date_description == 'next day' ) { 
	    return tribe_get_next_day_date(get_query_var('start_date'));
	}   
	return date('Y-m-d', strtotime($date_description) );
} 

old.php

<?php
/** 
* Get the date for the day navigation link
*
* @param string $date_description
* @return string
* @since 3.1.1
* @throws OverflowException
*/
function tribe_get_the_day_link_date( $date_description ) {
	if ( is_null($date_description) ) { 
	    return TribeEventsPro::instance()->todaySlug;
	}   
	if ( $date_description == 'previous day' ) { 
	    return tribe_get_previous_day_date(get_query_var('start_date'));
	}   
	if ( $date_description = 'next day' ) {
	    return tribe_get_next_day_date(get_query_var('start_date'));
	}   
	return date('Y-m-d', $date_description);
}

thanks