diff --git a/src/parser/calendar/data/PhutilCalendarRecurrenceRule.php b/src/parser/calendar/data/PhutilCalendarRecurrenceRule.php
--- a/src/parser/calendar/data/PhutilCalendarRecurrenceRule.php
+++ b/src/parser/calendar/data/PhutilCalendarRecurrenceRule.php
@@ -352,20 +352,15 @@
           break;
         case self::FREQUENCY_MONTHLY:
           $this->cursorMonth -= $interval;
-
-          while ($this->cursorMonth < 1) {
-            $this->rewindMonth();
-          }
+          $this->rewindMonth();
           break;
         case self::FREQUENCY_DAILY:
           $this->cursorDay -= $interval;
-
-          $week_start = $this->getWeekStart();
-          while ($this->cursorDay < 1) {
-            $year_map = $this->getYearMap($this->cursorYear, $week_start);
-            $this->cursorDay += $year_map['monthDays'][$this->cursorMonth];
-            $this->rewindMonth();
-          }
+          $this->rewindDay();
+          break;
+        case self::FREQUENCY_HOURLY:
+          $this->cursorHour -= $interval;
+          $this->rewindHour();
           break;
         default:
           throw new Exception(
@@ -1238,13 +1233,36 @@
     if ($scale < self::SCALE_MONTHLY) {
       $parts[] = $this->stateDay;
     }
+    if ($scale < self::SCALE_DAILY) {
+      $parts[] = $this->stateHour;
+    }
 
     return implode('/', $parts);
   }
 
   private function rewindMonth() {
-    $this->cursorYear--;
-    $this->cursorMonth += 12;
+    while ($this->cursorMonth < 1) {
+      $this->cursorYear--;
+      $this->cursorMonth += 12;
+    }
+  }
+
+  private function rewindDay() {
+    $week_start = $this->getWeekStart();
+    while ($this->cursorDay < 1) {
+      $year_map = $this->getYearMap($this->cursorYear, $week_start);
+      $this->cursorDay += $year_map['monthDays'][$this->cursorMonth];
+      $this->cursorMonth--;
+      $this->rewindMonth();
+    }
+  }
+
+  private function rewindHour() {
+    while ($this->cursorHour < 0) {
+      $this->cursorHour += 24;
+      $this->cursorDay--;
+      $this->rewindDay();
+    }
   }
 
   private function advanceCursorState(
diff --git a/src/parser/calendar/data/__tests__/PhutilCalendarRecurrenceRuleTestCase.php b/src/parser/calendar/data/__tests__/PhutilCalendarRecurrenceRuleTestCase.php
--- a/src/parser/calendar/data/__tests__/PhutilCalendarRecurrenceRuleTestCase.php
+++ b/src/parser/calendar/data/__tests__/PhutilCalendarRecurrenceRuleTestCase.php
@@ -853,6 +853,131 @@
       '19980101T020000Z',
     );
 
+    $tests[] = array(
+      'BYMONTHDAY' => array(1, 3),
+    );
+    $expect[] = array(
+      '19970903T000000Z',
+      '19970903T010000Z',
+      '19970903T020000Z',
+    );
+
+    $tests[] = array(
+      'BYMONTH' => array(1, 3),
+      'BYMONTHDAY' => array(5, 7),
+    );
+    $expect[] = array(
+      '19980105T000000Z',
+      '19980105T010000Z',
+      '19980105T020000Z',
+    );
+
+    $tests[] = array(
+      'BYDAY' => array('TU', 'TH'),
+    );
+    $expect[] = array(
+      '19970902T090000Z',
+      '19970902T100000Z',
+      '19970902T110000Z',
+    );
+
+    $tests[] = array(
+      'BYMONTH' => array(1, 3),
+      'BYDAY' => array('TU', 'TH'),
+    );
+    $expect[] = array(
+      '19980101T000000Z',
+      '19980101T010000Z',
+      '19980101T020000Z',
+    );
+
+    $tests[] = array(
+      'BYMONTHDAY' => array(1, 3),
+      'BYDAY' => array('TU', 'TH'),
+    );
+    $expect[] = array(
+      '19980101T000000Z',
+      '19980101T010000Z',
+      '19980101T020000Z',
+    );
+
+    $tests[] = array(
+      'BYMONTHDAY' => array(1, 3),
+      'BYMONTH' => array(1, 3),
+      'BYDAY' => array('TU', 'TH'),
+    );
+    $expect[] = array(
+      '19980101T000000Z',
+      '19980101T010000Z',
+      '19980101T020000Z',
+    );
+
+    $tests[] = array(
+      'COUNT' => 4,
+      'BYYEARDAY' => array(1, 100, 200, 365),
+    );
+    $expect[] = array(
+      '19971231T000000Z',
+      '19971231T010000Z',
+      '19971231T020000Z',
+      '19971231T030000Z',
+    );
+
+    $tests[] = array(
+      'COUNT' => 4,
+      'BYYEARDAY' => array(-365, -266, -166, -1),
+    );
+    $expect[] = array(
+      '19971231T000000Z',
+      '19971231T010000Z',
+      '19971231T020000Z',
+      '19971231T030000Z',
+    );
+
+    $tests[] = array(
+      'COUNT' => 4,
+      'BYMONTH' => array(4, 7),
+      'BYYEARDAY' => array(1, 100, 200, 365),
+    );
+    $expect[] = array(
+      '19980410T000000Z',
+      '19980410T010000Z',
+      '19980410T020000Z',
+      '19980410T030000Z',
+    );
+
+    $tests[] = array(
+      'COUNT' => 4,
+      'BYMONTH' => array(4, 7),
+      'BYYEARDAY' => array(-365, -266, -166, -1),
+    );
+    $expect[] = array(
+      '19980410T000000Z',
+      '19980410T010000Z',
+      '19980410T020000Z',
+      '19980410T030000Z',
+    );
+
+    $tests[] = array(
+      'BYHOUR' => array(6, 18),
+    );
+    $expect[] = array(
+      '19970902T180000Z',
+      '19970903T060000Z',
+      '19970903T180000Z',
+    );
+
+    $tests[] = array(
+      'BYMINUTE' => array(15, 45),
+      'BYSECOND' => array(15, 45),
+      'BYSETPOS' => array(3, -3),
+    );
+    $expect[] = array(
+      '19970902T091545Z',
+      '19970902T094515Z',
+      '19970902T101545Z',
+    );
+
     $this->assertRules(
       array(
         'FREQ' => 'HOURLY',