diff --git a/src/DateTime.php b/src/DateTime.php
index 5cdc35b..c57aa32 100644
--- a/src/DateTime.php
+++ b/src/DateTime.php
@@ -6,6 +6,7 @@
 
 use DateInterval;
 use DateTime as DateTimePhp;
+use DateTimeImmutable;
 use DateTimeZone;
 use Tuscanicz\DateTimeBundle\Date\Date;
 use Tuscanicz\DateTimeBundle\Time\Time;
@@ -53,6 +54,11 @@ public function toDateTime(): DateTimePhp
         return new DateTimePhp($this->toFormat('r'));
     }
 
+    public function toDateTimeImmutable(): DateTimeImmutable
+    {
+        return DateTimeImmutable::createFromMutable($this->toDateTime());
+    }
+
     public function isBetween(DateTime $start, DateTime $end): bool
     {
         $thisDateTime = $this->toDateTime();
diff --git a/src/DateTimeFactory.php b/src/DateTimeFactory.php
index af0243c..05113fc 100644
--- a/src/DateTimeFactory.php
+++ b/src/DateTimeFactory.php
@@ -5,6 +5,7 @@
 namespace Tuscanicz\DateTimeBundle;
 
 use DateTime as DateTimePhp;
+use DateTimeInterface;
 use DateTimeZone;
 use Tuscanicz\DateTimeBundle\Date\Date;
 use Tuscanicz\DateTimeBundle\Time\Time;
@@ -20,7 +21,7 @@ public function now(string $timezone = self::TIMEZONE_GMT): DateTime
         $timezonePhp = new DateTimeZone($timezone);
         $datetimePhp = new DateTimePhp('now', $timezonePhp);
 
-        return $this->fromDateTimePhp($datetimePhp, $timezone);
+        return $this->fromDateTimeInterface($datetimePhp, $timezone);
     }
 
     public function fromTimestamp(int $timestamp, string $timezone = self::TIMEZONE_GMT): DateTime
@@ -29,10 +30,10 @@ public function fromTimestamp(int $timestamp, string $timezone = self::TIMEZONE_
         $datetimePhp = new DateTimePhp('now', $timezonePhp);
         $datetimePhp->setTimestamp($timestamp);
 
-        return $this->fromDateTimePhp($datetimePhp, $timezone);
+        return $this->fromDateTimeInterface($datetimePhp, $timezone);
     }
 
-    private function fromDateTimePhp(DateTimePhp $dateTimePhp, string $timezone = DateTimeFactory::TIMEZONE_GMT): DateTime
+    public function fromDateTimeInterface(DateTimeInterface $dateTimePhp, string $timezone = DateTimeFactory::TIMEZONE_GMT): DateTime
     {
         return new DateTime(
             new Date(
diff --git a/tests/DateTimeFactoryTest.php b/tests/DateTimeFactoryTest.php
index 3e702c0..541dde5 100644
--- a/tests/DateTimeFactoryTest.php
+++ b/tests/DateTimeFactoryTest.php
@@ -4,6 +4,8 @@
 
 namespace Tuscanicz\DateTimeBundle;
 
+use DateTime as DateTimePhp;
+use DateTimeImmutable;
 use PHPUnit\Framework\TestCase;
 use Tuscanicz\DateTimeBundle\Date\Date;
 use Tuscanicz\DateTimeBundle\Time\Time;
@@ -36,4 +38,26 @@ public function testFromTimestamp(): void
 
         self::assertEquals($expectedDateTime, $dateTime);
     }
+
+    public function testFromDateTimeInterfaceWithDateTime(): void
+    {
+        $expectedDateTime = new DateTime(new Date(2009, 2, 13), new Time(23, 31, 30));
+        $dateTime = $this->dateTimeFactory->fromDateTimeInterface(
+            new DateTimePhp('2009-02-13 23:31:30'),
+            self::TIMEZONE_GMT
+        );
+
+        self::assertEquals($expectedDateTime, $dateTime);
+    }
+
+    public function testFromDateTimeInterfaceWithDateTimeImmutable(): void
+    {
+        $expectedDateTime = new DateTime(new Date(2009, 2, 13), new Time(23, 31, 30));
+        $dateTime = $this->dateTimeFactory->fromDateTimeInterface(
+            new DateTimeImmutable('2009-02-13 23:31:30'),
+            self::TIMEZONE_GMT
+        );
+
+        self::assertEquals($expectedDateTime, $dateTime);
+    }
 }
diff --git a/tests/DateTimeTest.php b/tests/DateTimeTest.php
index de87415..dcbfd55 100644
--- a/tests/DateTimeTest.php
+++ b/tests/DateTimeTest.php
@@ -4,6 +4,8 @@
 
 namespace Tuscanicz\DateTimeBundle;
 
+use DateTime as DateTimePhp;
+use DateTimeImmutable;
 use PHPUnit\Framework\TestCase;
 use Tuscanicz\DateTimeBundle\Date\Date;
 use Tuscanicz\DateTimeBundle\Time\Time;
@@ -85,7 +87,7 @@ public function testToTimestamp(): void
      * @param bool $expectedResult
      * @dataProvider isBetweenProvider
      */
-    public function testIsBetween(DateTime $now, DateTime $start, DateTime $end, bool $expectedResult)
+    public function testIsBetween(DateTime $now, DateTime $start, DateTime $end, bool $expectedResult): void
     {
         self::assertSame($expectedResult, $now->isBetween($start, $end));
     }
@@ -104,7 +106,7 @@ public function isBetweenProvider(): array
      * @param bool $expectedResult
      * @dataProvider isSameAsDataProvider
      */
-    public function testIsSameAs(DateTime $oneDateTime, DateTime $secondDateTime, bool $expectedResult)
+    public function testIsSameAs(DateTime $oneDateTime, DateTime $secondDateTime, bool $expectedResult): void
     {
         self::assertSame($expectedResult, $oneDateTime->isSameAs($secondDateTime));
     }
@@ -283,4 +285,30 @@ public function testAddMinutes(): void
 
         self::assertEquals($expectedNewDateTime, $newDateTime);
     }
+
+    public function testToDateTime(): void
+    {
+        $dateTime = new DateTime(
+            new Date(1987, 7, 31),
+            new Time(11, 19, 0)
+        );
+
+        $actualPhpDateTime = $dateTime->toDateTime();
+        $expectedNewDateTime = new DateTimePhp('1987-07-31 11:19:00');
+
+        self::assertEquals($expectedNewDateTime, $actualPhpDateTime);
+    }
+
+    public function testToDateTimeImmutable(): void
+    {
+        $dateTime = new DateTime(
+            new Date(1987, 7, 3),
+            new Time(11, 19, 3)
+        );
+
+        $actualPhpDateTime = $dateTime->toDateTimeImmutable();
+        $expectedNewDateTime = new DateTimeImmutable('1987-07-03 11:19:03');
+
+        self::assertEquals($expectedNewDateTime, $actualPhpDateTime);
+    }
 }