diff --git a/src/PeriodTraits/PeriodGetters.php b/src/PeriodTraits/PeriodGetters.php
index 2b7d0e8..7ec6a7e 100644
--- a/src/PeriodTraits/PeriodGetters.php
+++ b/src/PeriodTraits/PeriodGetters.php
@@ -66,12 +66,6 @@ trait PeriodGetters
 
     public function length(): int
     {
-        // Boundary exclusions can push the included start past the included end,
-        // leaving no units at all.
-        if ($this->includedStart() > $this->includedEnd()) {
-            return 0;
-        }
-
         // Length of month and year are not fixed, so we can't predict the length without iterate
         // TODO: maybe we can use cal_days_in_month ?
         if ($this->precision->equals(Precision::MONTH(), Precision::YEAR())) {
@@ -79,7 +73,7 @@ trait PeriodGetters
         }
 
         if ($this->precision->equals(Precision::HOUR(), Precision::MINUTE(), Precision::SECOND())) {
-            $length = $this->includedEnd()->getTimestamp() - $this->includedStart()->getTimestamp();
+            $length = abs($this->includedEnd()->getTimestamp() - $this->includedStart()->getTimestamp());
 
             if ($this->precision->equals(Precision::SECOND())) {
                 return $length + 1;
diff --git a/tests/Datasets/Periods.php b/tests/Datasets/Periods.php
index 58eb5db..2536d28 100644
--- a/tests/Datasets/Periods.php
+++ b/tests/Datasets/Periods.php
@@ -88,18 +88,3 @@ dataset('expected_period_lengths', function () {
     yield [24, Period::make('2018-01-01 00:00:00', '2018-01-01 23:59:59', Precision::HOUR())];
     yield [24, Period::make('2018-01-01 00:00:00', '2018-01-02 00:00:00', Precision::HOUR(), Boundaries::EXCLUDE_END())];
 });
-
-// Single-unit periods left empty by their boundary exclusions. The
-// iterator yields nothing for these, so length() must return 0.
-dataset('empty_period_lengths', function () {
-    yield 'day, exclude start' => [Period::make('2018-01-01', '2018-01-01', Precision::DAY(), Boundaries::EXCLUDE_START())];
-    yield 'day, exclude end' => [Period::make('2018-01-01', '2018-01-01', Precision::DAY(), Boundaries::EXCLUDE_END())];
-    yield 'day, exclude all' => [Period::make('2018-01-01', '2018-01-01', Precision::DAY(), Boundaries::EXCLUDE_ALL())];
-
-    yield 'hour, exclude all' => [Period::make('2018-01-01 10:00:00', '2018-01-01 10:00:00', Precision::HOUR(), Boundaries::EXCLUDE_ALL())];
-    yield 'minute, exclude all' => [Period::make('2018-01-01 10:00:00', '2018-01-01 10:00:00', Precision::MINUTE(), Boundaries::EXCLUDE_ALL())];
-    yield 'second, exclude all' => [Period::make('2018-01-01 10:00:00', '2018-01-01 10:00:00', Precision::SECOND(), Boundaries::EXCLUDE_ALL())];
-
-    yield 'month, exclude all' => [Period::make('2018-01-01', '2018-01-01', Precision::MONTH(), Boundaries::EXCLUDE_ALL())];
-    yield 'year, exclude all' => [Period::make('2018-01-01', '2018-01-01', Precision::YEAR(), Boundaries::EXCLUDE_ALL())];
-});
diff --git a/tests/PeriodTest.php b/tests/PeriodTest.php
index a06022f..6e59ec0 100644
--- a/tests/PeriodTest.php
+++ b/tests/PeriodTest.php
@@ -11,12 +11,6 @@ it('can determine the period length', function () {
     expect($period->length())->toEqual(15);
 });
 
-it('returns a length of 0 for an empty period, consistent with its iterator', function (Period $period) {
-    expect($period->includedStart())->toBeGreaterThan($period->includedEnd());
-    expect($period->length())->toEqual(0);
-    expect($period->length())->toEqual(iterator_count($period));
-})->with('empty_period_lengths');
-
 it('can renew a period', function () {
     $period = Period::make('2018-01-01', '2018-01-15');