Conditional display of start and end dates (PHP/Wordpress) - wordpress

Question

(As you can tell from this post I am not a programmer, so please help me to see if this is even possible... )
I want to improve the Start / End date display for events in Events Manager (plugin for WordPress)
At the moment the the end times will only show up if different then the start date (good!) but will be in the format:
1 January 2014 - 31 January 2014.
I would like it to display as: 1 - 31 January 2014.
That isn't too hard, but it becomes a little more complicated when events wrap or extend past a month, or a year.
Here are the different cases I am trying to achieve:
Start date only:
1 January 2014
Start and end date in same month
1 – 12 January 2014
Start and end date in different month but same year.
28 January – 3 February 2014
Start and end date in different months and different years.
31 December 2014 – 3 January 2015
Can anyone tell me
a) if this is at all possible to do with a function in the WordPress functions file?
and
b) point me in the right direction on how to do the conditioning?
I don't even know what to google for, so even that would be a help. (I am not expecting a fully working code example, although you are more then welcome to include that if you want!)
Update: Here is an example of a function that does some of this, but only in the style of the last case in my list above.
add_filter('em_event_output_placeholder','my_em_placeholder_mod_eventdates',1,3);
function my_em_placeholder_mod_eventdates($replace, $EM_Event, $result){
if ( $result == '#_EVENTDATES' ) {
if( $EM_Event->event_start_date != $EM_Event->event_end_date){
$replace = date_i18n('d M Y', $EM_Event->start).' - '. date_i18n('d M Y', $EM_Event->end);
}else{
$replace = date_i18n('d M Y', $EM_Event->start);
}
}
return $replace;
}
Update 2, with working code:
This code works for me at least.
add_filter('em_event_output_placeholder','my_em_placeholder_mod_eventdates',1,3);
function my_em_placeholder_mod_eventdates($replace, $EM_Event, $result){
if ( $result == '#_EVENTDATES' ) :
$sd = $EM_Event->start;
$ed = $EM_Event->end;
if (!empty ($ed) && $sd != $ed ) {
//Event has an end date and end date is different than start date
if (date('Y', $sd) == date('Y', $ed)) {
// Start and end are in same year
if (date('n', $sd) == date('n', $ed)) {
//Start and end are in the same month
$replace = date_i18n('j', $sd).'-'.date_i18n('j F Y', $ed);
if (date('j', $sd) == date('j', $ed)) {
//Start and end are on the same day
$replace = date_i18n('j F Y', $sd);
}
} else {
//Start and end are in different months
$replace = date_i18n('j F', $sd).' - '.date_i18n('j F Y', $ed);
}
} else {
//Start and end are in different years
$replace = date_i18n('j F Y', $sd).' - '. date_i18n('j F Y', $ed);
}
} else {
// No end date, or start and end date are the same
$replace = date_i18n('j F Y', $sd);
}
endif;
return $replace;
}

Answer 1

Try this:
add_filter('em_event_output_placeholder','my_em_placeholder_mod_eventdates',1,3);
function my_em_placeholder_mod_eventdates($replace, $EM_Event, $result){
if ( $result == '#_EVENTDATES' ) :
$sd = $EM_Event->event_start_date;
$ed = $EM_Event->event_end_date;
if (!empty ($ed) && $sd != $ed ) {
//Event has an end date and end date is different than start date
if (date('Y', $sd) == date('Y'. $ed) {
// Start and end are in same year
if (date('n', $sd) == date('n', $ed) {
//Start and end are in the same month
$replace = date_i18n('j', $sd).'-'.date_i18n('j F Y', $ed);
} else {
//Start and end are in different months
$replace = date_i18n('j F', $sd).' - '.date_i18n('j F Y', $ed);
}
} else {
//Start and end are in different years
$replace = date_i18n('j F Y', $sd).' - '. date_i18n('j F Y', $ed);
}
} else {
// No end date, or start and end date are the same
$replace = date_i18n('j F Y', $sd);
}
endif;
return $replace;
}