Convert a start and end timestamp into a nicely formatted and joined up date range

functions.php

<?php
/**
 * Filter for Unlimited Elements to format a date range, from two timestamps
 */
function filter_format_date_range($startTimeStamp, $endTimeStamp){
    $displayDate = "";

    if($startTimeStamp == $endTimeStamp) {
        // same date
        $displayDate = date('j M Y', $endTimeStamp);
    } else {
        $startDate = getDate($startTimeStamp);
        $endDate = getDate($endTimeStamp);

        if($startDate["year"] == $endDate["year"]) {
            if($startDate["mon"] == $endDate["mon"]) {
                // same year, same month
                $displayDate = date('j-', $startTimeStamp) . date('j M Y', $endTimeStamp);
            } else {
                // same year, diff month
                $displayDate = date('j M-', $startTimeStamp) . date('j M Y', $endTimeStamp);
            }
        } else {
            // different years, return full date range
            $displayDate = date('j M Y-', $startTimeStamp) . date('j M Y', $endTimeStamp);
        }
    }

    return $displayDate;
}
add_filter( 'format_date_range', 'filter_format_date_range', 10, 2 );

unlimited-elements.html

<!-- Unlimited Elements Twig Template -->
{% set startDate = getPostMeta(current_post.id,"start-date") %}
{% set endDate = getPostMeta(current_post.id,"end-date") %}
{% set formattedDate = apply_filters('format_date_range', startDate, endDate) %}
<div>{{formattedDate}}</div>