diff --git a/inc/RRule.php b/inc/RRule.php
index 61610c01..34c14e63 100644
--- a/inc/RRule.php
+++ b/inc/RRule.php
@@ -248,7 +248,7 @@ class RepeatRuleDateTime extends DateTime {
 //      $value_type = $date->GetParameterValue('VALUE');
 //      if ( isset($value_type) && $value_type == 'DATE' ) $this->is_date = true;
       $date = $actual_date;
-      if ( DEBUG_RRULE ) printf( "Date%s property%s: %s%s\n", ($this->is_date ? "" : "Time"),
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Date%s property%s: %s%s", ($this->is_date ? "" : "Time"),
               (isset($this->tzid) ? ' with timezone' : ''), $date,
               (isset($this->tzid) ? ' in '.$this->tzid : '') );
     }
@@ -267,7 +267,7 @@ class RepeatRuleDateTime extends DateTime {
         $dtz = self::$UTCzone;
         $this->tzid = null;
       }
-      if ( DEBUG_RRULE ) printf( "Date%s property%s: %s%s\n", ($this->is_date ? "" : "Time"),
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Date%s property%s: %s%s", ($this->is_date ? "" : "Time"),
               (isset($this->tzid) ? ' with timezone' : ''), $date,
               (isset($this->tzid) ? ' in '.$this->tzid : '') );
     }
@@ -278,7 +278,7 @@ class RepeatRuleDateTime extends DateTime {
       // Floating
       $dtz = self::$UTCzone;
       $this->tzid = null;
-      if ( DEBUG_RRULE ) printf( "Floating Date value: %s\n", $date );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Floating Date value: %s", $date );
     }
     elseif ( $dtz === null || $dtz == '' ) {
       $dtz = self::$UTCzone;
@@ -292,18 +292,18 @@ class RepeatRuleDateTime extends DateTime {
         }
       }
       $this->is_date = (strlen($date) == 8 );
-      if ( DEBUG_RRULE ) printf( "Date%s value with timezone 1: %s in %s\n", ($this->is_date?"":"Time"), $date, $this->tzid );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Date%s value with timezone 1: %s in %s", ($this->is_date?"":"Time"), $date, $this->tzid );
     }
     elseif ( is_string($dtz) ) {
       $dtz = new RepeatRuleTimeZone($dtz);
       $this->tzid = $dtz->tzid();
       $type = gettype($date);
-      if ( DEBUG_RRULE ) printf( "Date%s $type with timezone 2: %s in %s\n", ($this->is_date?"":"Time"), $date, $this->tzid );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Date%s $type with timezone 2: %s in %s", ($this->is_date?"":"Time"), $date, $this->tzid );
     }
     else {
       $this->tzid = $dtz->getName();
       $type = gettype($date);
-      if ( DEBUG_RRULE ) printf( "Date%s $type with timezone 3: %s in %s\n", ($this->is_date?"":"Time"), $date, $this->tzid );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Date%s $type with timezone 3: %s in %s", ($this->is_date?"":"Time"), $date, $this->tzid );
     }
 
     parent::__construct($date, $dtz);
@@ -648,7 +648,7 @@ class RepeatRule {
     $this->original_rule = $rrule;
 
     if ( DEBUG_RRULE ) {
-      printf( "Constructing RRULE based on: '%s', rrule: '%s' (float: %s)\n", $basedate, $rrule, ($return_floating_times ? "yes" : "no") );
+      dbg_error_log( 'RRULE', "Constructing RRULE based on: '%s', rrule: '%s' (float: %s)", $basedate, $rrule, ($return_floating_times ? "yes" : "no") );
     }
 
     if ( preg_match('{FREQ=([A-Z]+)(;|$)}', $rrule, $m) ) $this->freq = $m[1];
@@ -688,7 +688,7 @@ class RepeatRule {
         /** need to handle the error, but FREQ is mandatory so unlikely */
     }
     $this->frequency_string = sprintf('+%d %s', $this->interval, $freq_name );
-    if ( DEBUG_RRULE ) printf( "Frequency modify string is: '%s', base is: '%s', TZ: %s\n", $this->frequency_string, $this->base->format('c'), $this->base->getTimeZone() );
+    if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Frequency modify string is: '%s', base is: '%s', TZ: %s", $this->frequency_string, $this->base->format('c'), $this->base->getTimeZone() );
     $this->Start($return_floating_times);
   }
 
@@ -735,7 +735,7 @@ class RepeatRule {
     if ( !$this->valid() ) return null;
     if ( !isset($this->instances[$this->position]) ) $this->GetMoreInstances($return_floating_times);
     if ( !$this->valid() ) return null;
-    if ( DEBUG_RRULE ) printf( "Returning date from position %d: %s (%s)\n", $this->position,
+    if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Returning date from position %d: %s (%s)", $this->position,
                           $this->instances[$this->position]->format('c'), $this->instances[$this->position]->FloatOrUTC($return_floating_times) );
     return $this->instances[$this->position];
   }
@@ -754,10 +754,9 @@ class RepeatRule {
   public function valid() {
     if ( DEBUG_RRULE && isset($this->instances[$this->position])) {
       $current = $this->instances[$this->position];
-      print "TimeZone: " . $current->getTimeZone() . "\n";
-      print "Date: " . $current->format('r') . "\n";
-      print "Errors:\n";
-      print_r($current->getLastErrors());
+      dbg_error_log( 'RRULE', "TimeZone: " . $current->getTimeZone());
+      dbg_error_log( 'RRULE', "Date: " . $current->format('r'));
+      dbg_log_array( 'RRULE', "Errors:", $current->getLastErrors());
     }
     if ( isset($this->instances[$this->position]) || !$this->finished ) return true;
     return false;
@@ -814,7 +813,7 @@ class RepeatRule {
         $this->current_base->modify( $this->frequency_string );
       }
       if ( $return_floating_times ) $this->current_base->setAsFloat();
-      if ( DEBUG_RRULE ) printf( "Getting more instances from: '%s' - %d, TZ: %s\n", $this->current_base->format('c'), count($this->instances), $this->current_base->getTimeZone() );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Getting more instances from: '%s' - %d, TZ: %s", $this->current_base->format('c'), count($this->instances), $this->current_base->getTimeZone() );
       $this->current_set = array( clone($this->current_base) );
       foreach( self::rrule_expand_limit($this->freq) AS $bytype => $action ) {
         if ( isset($this->{$bytype}) ) {
@@ -827,7 +826,7 @@ class RepeatRule {
       if ( isset($this->bysetpos) ) $this->limit_bysetpos();
 
       $position = count($this->instances) - 1;
-      if ( DEBUG_RRULE ) printf( "Inserting %d from current_set into position %d\n", count($this->current_set), $position + 1 );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Inserting %d from current_set into position %d", count($this->current_set), $position + 1 );
       foreach( $this->current_set AS $k => $instance ) {
         if ( $instance < $this->base ) continue;
         if ( isset($this->until) && $instance > $this->until ) {
@@ -842,7 +841,7 @@ class RepeatRule {
             return;
           }
           $this->instances[$position] = $instance;
-          if ( DEBUG_RRULE ) printf( "Added date %s into position %d in current set\n", $instance->format('c'), $position );
+          if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Added date %s into position %d in current set", $instance->format('c'), $position );
         }
       }
     }
@@ -888,7 +887,7 @@ class RepeatRule {
     foreach( $instances AS $k => $instance ) {
       foreach( $this->bymonth AS $k => $month ) {
         $expanded = $this->date_mask( clone($instance), null, $month, null, null, null, null);
-        if ( DEBUG_RRULE ) printf( "Expanded BYMONTH $month into date %s\n", $expanded->format('c') );
+        if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYMONTH $month into date %s", $expanded->format('c') );
         $this->current_set[] = $expanded;
       }
     }
@@ -901,10 +900,10 @@ class RepeatRule {
       foreach( $this->bymonthday AS $k => $monthday ) {
         $expanded = $this->date_mask( clone($instance), null, null, $monthday, null, null, null);
         if ($monthday == -1 || $expanded->format('d') == $monthday) {
-          if ( DEBUG_RRULE ) printf( "Expanded BYMONTHDAY $monthday into date %s from %s\n", $expanded->format('c'), $instance->format('c') );
+          if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYMONTHDAY $monthday into date %s from %s", $expanded->format('c'), $instance->format('c') );
           $this->current_set[] = $expanded;
         } else {
-          if ( DEBUG_RRULE ) printf( "Expanded BYMONTHDAY $monthday into date %s from %s, which is not the same day of month, skipping.\n", $expanded->format('c'), $instance->format('c') );
+          if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYMONTHDAY $monthday into date %s from %s, which is not the same day of month, skipping.", $expanded->format('c'), $instance->format('c') );
         }
       }
     }
@@ -940,7 +939,7 @@ class RepeatRule {
       $expanded = clone($day_in_week);
       $expanded->modify( sprintf('+%d day', $offset) );
       $this->current_set[] = $expanded;
-      if ( DEBUG_RRULE ) printf( "Expanded BYDAY(W) $weekday into date %s\n", $expanded->format('c') );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYDAY(W) $weekday into date %s", $expanded->format('c') );
     }
   }
 
@@ -955,7 +954,7 @@ class RepeatRule {
         $dow = self::rrule_day_number($matches[3]);
         $first_dom = 1 + $dow - $dow_of_first;  if ( $first_dom < 1 ) $first_dom +=7;  // e.g. 1st=WE, dow=MO => 1+1-3=-1 => MO is 6th, etc.
         $whichweek = intval($matches[2]);
-        if ( DEBUG_RRULE ) printf( "Expanding BYDAY(M) $weekday in month of %s\n", $first_of_month->format('c') );
+        if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanding BYDAY(M) $weekday in month of %s", $first_of_month->format('c') );
         if ( $whichweek > 0 ) {
           $whichweek--;
           $monthday = $first_dom;
@@ -969,14 +968,14 @@ class RepeatRule {
           }
           if ( $monthday > 0 && $monthday <= $days_in_month ) {
             $expanded = $this->date_mask( clone($day_in_month), null, null, $monthday, null, null, null);
-            if ( DEBUG_RRULE ) printf( "Expanded BYDAY(M) $weekday now $monthday into date %s\n", $expanded->format('c') );
+            if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYDAY(M) $weekday now $monthday into date %s", $expanded->format('c') );
             $this->current_set[] = $expanded;
           }
         }
         else {
           for( $monthday = $first_dom; $monthday <= $days_in_month; $monthday += 7 ) {
             $expanded = $this->date_mask( clone($day_in_month), null, null, $monthday, null, null, null);
-            if ( DEBUG_RRULE ) printf( "Expanded BYDAY(M) $weekday now $monthday into date %s\n", $expanded->format('c') );
+            if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYDAY(M) $weekday now $monthday into date %s", $expanded->format('c') );
             $this->current_set[] = $expanded;
           }
         }
@@ -996,7 +995,7 @@ class RepeatRule {
         $dow = self::rrule_day_number($matches[3]);
         $first_doy = 1 + $dow - $dow_of_first;  if ( $first_doy < 1 ) $first_doy +=7;  // e.g. 1st=WE, dow=MO => 1+1-3=-1 => MO is 6th, etc.
         $whichweek = intval($matches[2]);
-        if ( DEBUG_RRULE ) printf( "Expanding BYDAY(Y) $weekday from date %s\n", $instance->format('c') );
+        if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanding BYDAY(Y) $weekday from date %s", $instance->format('c') );
         if ( $whichweek > 0 ) {
           $whichweek--;
           $yearday = $first_doy;
@@ -1010,14 +1009,14 @@ class RepeatRule {
           }
           if ( $yearday > 0 && $yearday <= $days_in_year ) {
             $expanded->modify(sprintf('+%d day', $yearday - 1));
-            if ( DEBUG_RRULE ) printf( "Expanded BYDAY(Y) $weekday now $yearday into date %s\n", $expanded->format('c') );
+            if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYDAY(Y) $weekday now $yearday into date %s", $expanded->format('c') );
             $this->current_set[] = $expanded;
           }
         }
         else {
           $expanded->modify(sprintf('+%d day', $first_doy - 1));
           for( $yearday = $first_doy; $yearday <= $days_in_year; $yearday += 7 ) {
-            if ( DEBUG_RRULE ) printf( "Expanded BYDAY(Y) $weekday now $yearday into date %s\n", $expanded->format('c') );
+            if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Expanded BYDAY(Y) $weekday now $yearday into date %s", $expanded->format('c') );
             $this->current_set[] = clone($expanded);
             $expanded->modify('+1 week');
           }
@@ -1095,7 +1094,7 @@ class RepeatRule {
     $this->current_set = array();
     foreach( $instances AS $k => $instance ) {
       foreach( $this->{$element_name} AS $k => $element_value ) {
-        if ( DEBUG_RRULE ) printf( "Limiting '$fmt_char' on '%s' => '%s' ?=? '%s' ? %s\n", $instance->format('c'), $instance->format($fmt_char), $element_value, ($instance->format($fmt_char) == $element_value ? 'Yes' : 'No') );
+        if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Limiting '$fmt_char' on '%s' => '%s' ?=? '%s' ? %s", $instance->format('c'), $instance->format($fmt_char), $element_value, ($instance->format($fmt_char) == $element_value ? 'Yes' : 'No') );
         if ( $instance->format($fmt_char) == $element_value ) $this->current_set[] = $instance;
       }
     }
@@ -1108,7 +1107,7 @@ class RepeatRule {
     foreach( $this->byday AS $k => $weekday ) {
       $dow = self::rrule_day_number($weekday);
       foreach( $instances AS $k => $instance ) {
-        if ( DEBUG_RRULE ) printf( "Limiting '$fmt_char' on '%s' => '%s' ?=? '%s' (%d) ? %s\n", $instance->format('c'), $instance->format($fmt_char), $weekday, $dow, ($instance->format($fmt_char) == $dow ? 'Yes' : 'No') );
+        if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Limiting '$fmt_char' on '%s' => '%s' ?=? '%s' (%d) ? %s", $instance->format('c'), $instance->format($fmt_char), $weekday, $dow, ($instance->format($fmt_char) == $dow ? 'Yes' : 'No') );
         if ( $instance->format($fmt_char) == $dow ) $this->current_set[] = $instance;
       }
     }
@@ -1127,7 +1126,7 @@ class RepeatRule {
     $count = count($instances);
     $this->current_set = array();
     foreach( $this->bysetpos AS $k => $element_value ) {
-      if ( DEBUG_RRULE ) printf( "Limiting bysetpos %s of %d instances\n", $element_value, $count );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Limiting bysetpos %s of %d instances", $element_value, $count );
       if ( $element_value > 0 ) {
         $this->current_set[] = $instances[$element_value - 1];
       }
@@ -1199,20 +1198,20 @@ function rrule_expand( $dtstart, $property, $component, $range_end, $is_date=nul
   if ( $return_floating_times ) $this_start->setAsFloat();
 
 //  if ( DEBUG_RRULE ) print_r( $this_start );
-  if ( DEBUG_RRULE ) printf( "RRULE: %s (floating: %s)\n", $recur, ($return_floating_times?"yes":"no") );
+  if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "%s (floating: %s)", $recur, ($return_floating_times?"yes":"no") );
   $rule = new RepeatRule( $this_start, $recur, $is_date, $return_floating_times );
   $i = 0;
 
   if ( !isset($c->rrule_expansion_limit) ) $c->rrule_expansion_limit = 5000;
   while( $date = $rule->next($return_floating_times) ) {
-//    if ( DEBUG_RRULE ) printf( "[%3d] %s\n", $i, $date->UTC() );
+//    if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "[%3d] %s", $i, $date->UTC() );
     $expansion[$date->FloatOrUTC($return_floating_times)] = $component;
     if ( $date > $range_end ) break;
     if ( $i++ >= $c->rrule_expansion_limit ) {
       dbg_error_log( 'ERROR', "Hit rrule expansion limit of ".$c->rrule_expansion_limit." on %s %s - increase rrule_expansion_limit in config to avoid events missing from freebusy", $component->GetType(), $component->GetProperty('UID'));
     }
   }
-//  if ( DEBUG_RRULE ) print_r( $expansion );
+//  if ( DEBUG_RRULE ) dbg_log_array( 'RRULE', 'expansion', $expansion );
   return $expansion;
 }
 
@@ -1290,7 +1289,7 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
       if ( !isset($dtstart_prop) ) continue;
       $dtstart = new RepeatRuleDateTime( $dtstart_prop );
       if ( $return_floating_times ) $dtstart->setAsFloat();
-      if ( DEBUG_RRULE ) printf( "Component is: %s (floating: %s)\n", $comp->GetType(), ($return_floating_times?"yes":"no") );
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Component is: %s (floating: %s)", $comp->GetType(), ($return_floating_times?"yes":"no") );
       $is_date = $dtstart->isDate();
       $instances[$dtstart->FloatOrUTC($return_floating_times)] = $comp;
       $rrule = $comp->GetProperty('RRULE');
@@ -1304,7 +1303,7 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
       $recur_utc = $recur_utc->FloatOrUTC($return_floating_times);
       if ( isset($range) && $range == 'THISANDFUTURE' ) {
         foreach( $instances AS $k => $v ) {
-          if ( DEBUG_RRULE ) printf( "Removing overridden instance at: $k\n" );
+          if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Removing overridden instance at: $k" );
           if ( $k >= $recur_utc ) unset($instances[$k]);
         }
       }
@@ -1319,39 +1318,35 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
       $summary = ( isset($p) ? $p->Value() : 'not set');
       $p =  $comp->GetProperty('UID');
       $uid = ( isset($p) ? $p->Value() : 'not set');
-      printf( "Processing event '%s' with UID '%s' starting on %s\n",
+      dbg_error_log( 'RRULE', "Processing event '%s' with UID '%s' starting on %s",
                  $summary, $uid, $dtstart->FloatOrUTC($return_floating_times) );
-      print( "Instances at start");
+      dbg_error_log( 'RRULE', "Instances at start");
       foreach( $instances AS $k => $v ) {
-        print ' : '.$k;
+        dbg_error_log( 'RRULE', ' : '.$k);
       }
-      print "\n";
     }
     $instances += rrule_expand($dtstart, 'RRULE', $comp, $range_end, null, $return_floating_times, $fallback_tzid);
     if ( DEBUG_RRULE ) {
-      print( "After rrule_expand");
+      dbg_error_log( 'RRULE', "After rrule_expand");
       foreach( $instances AS $k => $v ) {
-        print ' : '.$k;
+        dbg_error_log ('RRULE', ' : '.$k);
       }
-      print "\n";
     }
     $instances += rdate_expand($dtstart, 'RDATE', $comp, $range_end, null, $return_floating_times);
     if ( DEBUG_RRULE ) {
-      print( "After rdate_expand");
+      dbg_error_log( 'RRULE', "After rdate_expand");
       foreach( $instances AS $k => $v ) {
-        print ' : '.$k;
+        dbg_error_log ('RRULE', ' : '.$k);
       }
-      print "\n";
     }
     foreach ( rdate_expand($dtstart, 'EXDATE', $comp, $range_end, null, $return_floating_times) AS $k => $v ) {
       unset($instances[$k]);
     }
     if ( DEBUG_RRULE ) {
-      print( "After exdate_expand");
+      dbg_error_log( 'RRULE', "After exdate_expand");
       foreach( $instances AS $k => $v ) {
-        print ' : '.$k;
+        dbg_error_log( 'RRULE', ' : '.$k);
       }
-      print "\n";
     }
   }
 
@@ -1362,7 +1357,7 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
   $end_utc = $range_end->FloatOrUTC($return_floating_times);
   foreach( $instances AS $utc => $comp ) {
     if ( $utc > $end_utc ) {
-      if ( DEBUG_RRULE ) printf( "We're done: $utc is out of the range.\n");
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "We're done: $utc is out of the range.");
       break;
     }
 
@@ -1393,7 +1388,7 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
     if ( $utc < $start_utc ) {
       if ( isset($early_start) && isset($last_duration) && $duration->equals($last_duration) ) {
         if ( $utc < $early_start ) {
-          if ( DEBUG_RRULE ) printf( "Next please: $utc is before $early_start and before $start_utc.\n");
+          if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Next please: $utc is before $early_start and before $start_utc.");
           continue;
         }
       }
@@ -1404,7 +1399,7 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
         $early_start = $latest_start->FloatOrUTC($return_floating_times);
         $last_duration = $duration;
         if ( $utc < $early_start ) {
-          if ( DEBUG_RRULE ) printf( "Another please: $utc is before $early_start and before $start_utc.\n");
+          if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Another please: $utc is before $early_start and before $start_utc.");
           continue;
         }
       }
@@ -1460,7 +1455,7 @@ function expand_event_instances( vComponent $vResource, $range_start = null, $ra
 
       if ( !isset($new_components[$recurrence_id]) && $dtend < $start_utc ) continue; // End before start of range: skip that too.
 
-      if ( DEBUG_RRULE ) printf( "Replacing overridden instance at %s\n", $recurrence_id);
+      if ( DEBUG_RRULE ) dbg_error_log( 'RRULE', "Replacing overridden instance at %s", $recurrence_id);
       $new_components[$recurrence_id] = $comp;
     }
   }