diff --git a/Tests/test.php b/Tests/test.php
index 705887e..26574fa 100644
--- a/Tests/test.php
+++ b/Tests/test.php
@@ -10,19 +10,25 @@ $timer->start();
 sleep(3);
 
 $timer->step('sleep 1');
-echo $timer->getLastStepRelativeDuration()->toUserString() . PHP_EOL;
-echo $timer->getLastStepDuration() . PHP_EOL;
+echo 'sleep 1' . PHP_EOL;
+echo "\t" . $timer->getLastStepRelativeDuration() . PHP_EOL;
+echo "\t" . $timer->getLastStepDuration() . PHP_EOL;
 
 sleep(2);
 
 $timer->step('sleep 2');
-echo $timer->getLastStepRelativeDuration()->toUserString() . PHP_EOL;
-echo $timer->getLastStepDuration() . PHP_EOL;
-$timer->stop();
+echo 'sleep 2' . PHP_EOL;
+echo "\t" . $timer->getLastStepRelativeDuration() . PHP_EOL;
+echo "\t" . $timer->getLastStepDuration() . PHP_EOL;
+
+sleep(3);
 
-$final = $timer->getDuration();
-echo $timer->getRelativeDuration()->toUserString() . PHP_EOL;
-echo $timer->getRelativeDuration() . PHP_EOL;
+$timer->step('sleep 3');
+echo 'sleep 3' . PHP_EOL;
+echo "\t" . $timer->getLastStepRelativeDuration() . PHP_EOL;
+echo "\t" . $timer->getLastStepDuration() . PHP_EOL;
 
-echo $timer->getDuration()->toUserString() . PHP_EOL;
-echo $timer->getDuration() . PHP_EOL;
\ No newline at end of file
+$timer->stop();
+echo 'STOP' . PHP_EOL;
+echo "\t" . $timer->getRelativeDuration() . PHP_EOL;
+echo "\t" . $timer->getDuration() . PHP_EOL;
\ No newline at end of file
diff --git a/src/ExecutionTimer/Duration.php b/src/ExecutionTimer/Duration.php
index 2667c51..a60a060 100644
--- a/src/ExecutionTimer/Duration.php
+++ b/src/ExecutionTimer/Duration.php
@@ -29,11 +29,10 @@ class Duration {
      */
     public function __toString () {
         return $this->getDays()->asRelativeWhole() . ' '
-            . $this->getHours()->asRelativeWhole() . ':'
-            . $this->getMinutes()->asRelativeWhole() . ':'
-            . $this->getSeconds()->asRelativeWhole() . '.'
-            . $this->getMilliseconds()->asRelativeWhole()
-            . $this->getMicroseconds()->asRelativeWhole();
+               . str_pad($this->getHours()->asRelativeWhole(), mb_strlen($this->getHours()->getUnitMax()), '0', STR_PAD_LEFT) . ':'
+               . str_pad($this->getMinutes()->asRelativeWhole(), mb_strlen($this->getMinutes()->getUnitMax()), '0', STR_PAD_LEFT) . ':'
+               . str_pad($this->getSeconds()->asRelativeWhole(), mb_strlen($this->getSeconds()->getUnitMax()), '0', STR_PAD_LEFT) . '.'
+               . str_pad($this->getMilliseconds()->asRelativeWhole(), mb_strlen($this->getMilliseconds()->getUnitMax()), '0', STR_PAD_LEFT);
     }
     /**
      * Convert duration to user friendly string
diff --git a/src/ExecutionTimer/DurationUnit.php b/src/ExecutionTimer/DurationUnit.php
index 6ee8119..5574e74 100644
--- a/src/ExecutionTimer/DurationUnit.php
+++ b/src/ExecutionTimer/DurationUnit.php
@@ -47,6 +47,14 @@ class DurationUnit {
         $this->unit_max = $units_max[$unit];
     }
 
+    /**
+     * The time unit
+     *
+     * @return int The maximum value of time unit
+     */
+    public function getUnit () {
+        return $this->unit;
+    }
     /**
      * The maximum value of time unit
      *
@@ -55,8 +63,8 @@ class DurationUnit {
      *
      * @return int The maximum value of time unit
      */
-    public function getUnit () {
-        return $this->unit;
+    public function getUnitMax () {
+        return $this->unit_max;
     }
 
     /**