diff --git a/CHANGELOG.md b/CHANGELOG.md
index 46b1273..d9270e1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,14 +18,19 @@ Security - in case of vulnerabilities.
 
 _TBD_
 
+## [0.4.0] 2018-02-16
+
+### Added
+- Added new method `getTimestampInterval` to returns duration in seconds ([#18](../../pull/18)).
+
 ## [0.3.0] 2017-11-18
 
 ### Added
-- Added new methods `getInterval`, `getPeriod`, `split`
-- Added `DateRangeProvider` interface and basic provider `FiniteDateRangeProvider`
+- Added `DateRangeProvider` interface and basic provider `FiniteDateRangeProvider` ([#13](../../pull/13)).
+- Added new method `getDateInterval`, `getDatePeriod`, `split` ([#9](../../pull/9)).
 
 ### Changed
-- Rename methods from using `time` ot `date`.
+- Rename methods from using `time` ot `date` ([#11](../../pull/11)).
 - Refactored internals.
 
 ## [0.1.1] 2017-11-17
diff --git a/README.md b/README.md
index d4ac9b8..b2652fb 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,8 @@ $range->isEnded();
 $range->isStartedOn(new DateTime());
 // Checking if range ended on specific date
 $range->isEndedOn(new DateTime());
+// Accessing range duration in seconds
+$range->getTimestampInterval();
 // Accessing range interval
 $range->getDateInterval()->format('%s');
 // Printing
diff --git a/src/DateRange.php b/src/DateRange.php
index 2652587..d7250c0 100644
--- a/src/DateRange.php
+++ b/src/DateRange.php
@@ -190,6 +190,14 @@ public function isEnded(): bool
         return $this->hasEndDate() && $this->state->compareEndDate(new DateTimeImmutable()) < 0;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getTimestampInterval(): int
+    {
+        return $this->getEndDate()->getTimestamp() - $this->getStartDate()->getTimestamp();
+    }
+
     /**
      * {@inheritdoc}
      */
diff --git a/src/DateRangeInterface.php b/src/DateRangeInterface.php
index fcc5ecf..61925c7 100644
--- a/src/DateRangeInterface.php
+++ b/src/DateRangeInterface.php
@@ -112,6 +112,13 @@ public function isStarted(): bool;
      */
     public function isEnded(): bool;
 
+    /**
+     * Returns the range duration in seconds.
+     *
+     * @return int
+     */
+    public function getTimestampInterval(): int;
+
     /**
      * Returns the range interval.
      *
diff --git a/tests/DateRangeTest.php b/tests/DateRangeTest.php
index e009e5b..f07f834 100644
--- a/tests/DateRangeTest.php
+++ b/tests/DateRangeTest.php
@@ -111,6 +111,19 @@ public function dumpRange()
         self::assertNotContains('state', $dump);
     }
 
+    /**
+     * @test
+     */
+    public function getTimestampInterval()
+    {
+        $now = new DateTimeImmutable();
+        $oneHourRange = new DateRange($now, $now->add(new DateInterval('PT1H')));
+        $oneDayRange = new DateRange($now, $now->add(new DateInterval('P1D')));
+
+        self::assertSame(3600, $oneHourRange->getTimestampInterval());
+        self::assertSame(86400, $oneDayRange->getTimestampInterval());
+    }
+
     /**
      * @test
      */