diff --git a/lib/olson.php b/lib/olson.php
index ebb2eaf4358..3506b4a8ba0 100644
--- a/lib/olson.php
+++ b/lib/olson.php
@@ -36,68 +36,152 @@ function olson_simple_rule_parser ($filename) {
              $save,
              $letter) = $rule;
 
-        
-        $id = $name;
-        if ($save === '0') {
-            $id .= '-reset';
-        } else {
-            $id .= '-set';
+        $srs = ($save === '0') ? 'reset' : 'set';
+
+        if(intval($to) == 0) {
+            $to = $from;
         }
 
-        if (isset($rules[$id])) {
-            if ($rules[$id][2] < $from) {
-                $rules[$id] = $rule;
-            }
-        } else {
-            $rules[$id] = $rule;
+        for($i = $from; $i <= $to; ++$i) {
+            $rules[$name][$i][$srs] = $rule;
         }
+        
     }
 
+    $months = array('jan' => 1, 'feb' => 2, 'mar' => 3, 'apr' =>  4, 'may' =>  5, 'jun' =>  6,
+                    'jul' => 7, 'aug' => 8, 'sep' => 9, 'oct' => 10, 'nov' => 11, 'dec' => 12);
+    $days = array('sun' => 0, 'mon' => 1, 'tue' => 2, 'wed' => 3, 'thu' => 4, 'fri' => 5, 'sat' => 6);
+
     // now reformat it a bit to match Moodle's DST table
     $moodle_rules = array();
-    foreach (array_keys($rules) as $rule) {
-        if (preg_match('/-reset$/', $rule)) {
-            continue; // we skip these
+    foreach ($rules as $family => $rulesbyyear) {
+        foreach ($rulesbyyear as $year => $rulesthisyear) {
+
+            if(!isset($rulesthisyear['set']) || !isset($rulesthisyear['reset'])) {
+                // What are we supposed to do with this???
+                print_object($family.' - '.$year.' was rejected');
+                continue;
+            }
+
+            list($discard,
+                 $name,
+                 $from,
+                 $to,
+                 $type,
+                 $in,
+                 $on,
+                 $at,
+                 $save,
+                 $letter) = $rulesthisyear['set'];
+    
+            $moodle_rule = array();
+    
+            list($hours, $mins) = explode(':', $save);
+            $save = $hours * 60 + $mins;
+            list($hours, $mins) = explode(':', $at);
+            $at = sprintf('%02d:%02d', $hours, $mins);
+            $in = strtolower($in);
+            if(!isset($months[$in])) {
+                error('Unknown month: '.$in);
+            }
+    
+            $moodle_rule['family'] = $name;
+            $moodle_rule['year'] = $year;
+            $moodle_rule['apply_offset']   = $save; // time offset
+
+            $moodle_rule['activate_month'] = $months[$in]; // the month
+            $moodle_rule['activate_time']  = $at; // the time
+
+            // Encode index and day as per Moodle's specs
+            if(is_numeric($on)) {
+                $moodle_rule['activate_index'] = $on;
+                $moodle_rule['activate_day']   = -1;
+            }
+            else {
+                $on = strtolower($on);
+                if(substr($on, 0, 4) == 'last') {
+                    // e.g. lastSun
+                    if(!isset($days[substr($on, 4)])) {
+                        error('Unknown last weekday: '.substr($on, 4));
+                    }
+                    else {
+                        $moodle_rule['activate_index'] = -1;
+                        $moodle_rule['activate_day']   = $days[substr($on, 4)];
+                    }
+                }
+                else if(substr($on, 3, 2) == '>=') {
+                    // e.g. Sun>=8
+                    if(!isset($days[substr($on, 0, 3)])) {
+                        error('Unknown last weekday: '.substr($on, 0, 3));
+                    }
+                    else {
+                        $moodle_rule['activate_index'] = substr($on, 5);
+                        $moodle_rule['activate_day']   = $days[substr($on, 0, 3)];
+                    }
+                }
+                else {
+                    error('unknown on '.$on);
+                }
+            }
+
+            // and now the "deactivate" data
+            list($discard,
+                 $name,
+                 $from,
+                 $to,
+                 $type,
+                 $in,
+                 $on,
+                 $at,
+                 $save,
+                 $letter) = $rulesthisyear['reset'];
+    
+            list($hours, $mins) = explode(':', $at);
+            $at = sprintf('%02d:%02d', $hours, $mins);
+            $in = strtolower($in);
+            if(!isset($months[$in])) {
+                error('Unknown month: '.$in);
+            }
+
+            $moodle_rule['deactivate_month'] = $months[$in]; // the month
+            $moodle_rule['deactivate_time']  = $at; // the time
+    
+            // Encode index and day as per Moodle's specs
+            if(is_numeric($on)) {
+                $moodle_rule['deactivate_index'] = $on;
+                $moodle_rule['deactivate_day']   = -1;
+            }
+            else {
+                $on = strtolower($on);
+                if(substr($on, 0, 4) == 'last') {
+                    // e.g. lastSun
+                    if(!isset($days[substr($on, 4)])) {
+                        error('Unknown last weekday: '.substr($on, 4));
+                    }
+                    else {
+                        $moodle_rule['deactivate_index'] = -1;
+                        $moodle_rule['deactivate_day']   = $days[substr($on, 4)];
+                    }
+                }
+                else if(substr($on, 3, 2) == '>=') {
+                    // e.g. Sun>=8
+                    if(!isset($days[substr($on, 0, 3)])) {
+                        error('Unknown last weekday: '.substr($on, 0, 3));
+                    }
+                    else {
+                        $moodle_rule['deactivate_index'] = substr($on, 5);
+                        $moodle_rule['deactivate_day']   = $days[substr($on, 0, 3)];
+                    }
+                }
+                else {
+                    error('unknown on '.$on);
+                }
+            }
+    
+            $moodle_rules[] = $moodle_rule;
+            print_object($moodle_rule);
         }
 
-        list($discard,
-             $name,
-             $from,
-             $to,
-             $type,
-             $in,
-             $on,
-             $at,
-             $save,
-             $letter) = $rules[$rule];
-
-        $moodle_rule = array();
-        $moodle_rule['name'] = $name;
-        $moodle_rule['apply_offset']   = $save; // time offset
-        $moodle_rule['activate_index'] = $on; // the weeknumber 
-        $moodle_rule['activate_day']   = $on; // the weekday
-        $moodle_rule['activate_month'] = $in; // the month
-        $moodle_rule['activate_time']  = $at; // the weeknumber
-
-        // and now the "deactivate" data
-        list($discard,
-             $name,
-             $from,
-             $to,
-             $type,
-             $in,
-             $on,
-             $at,
-             $save,
-             $letter) = $rules[$name.'-reset'];
-
-        $moodle_rule['deactivate_index'] = $on; // the weeknumber 
-        $moodle_rule['deactivate_day']   = $on; // the weekday
-        $moodle_rule['deactivate_month'] = $in; // the month
-        $moodle_rule['deactivate_time']  = $at; // the weeknumber
-
-        $moodle_rules[$name] = $moodle_rule;
-
     }
 
     return $moodle_rules;