Make !!startdate!! and !!enddate!! available for all Paid Memberships Pro emails.

my_pmpro_email_data.php

/*
	Make !!startdate!! and !!enddate!! available for all PMPro emails.

	Add this code to a custom plugin.
*/
function my_pmpro_email_data($data, $email) {	
	$user = get_user_by("login", $data['user_login']);

	$level = pmpro_getMembershipLevelForUser($user->ID);

	if(!empty($level->startdate))  
		$data['startdate'] =  date_i18n(get_option('date_format'), $level->startdate);
	else
		$data['startdate'] = '';

	if(!empty($level->enddate))
		$data['enddate'] = date_i18n(get_option('date_format'), $level->enddate);
	else
		$data['enddate'] = '';

	return $data;
}
add_filter("pmpro_email_data", "my_pmpro_email_data", 10, 2);