diff --git a/src/Recurr/Rule.php b/src/Recurr/Rule.php
index dfcf40f..c75e088 100644
--- a/src/Recurr/Rule.php
+++ b/src/Recurr/Rule.php
@@ -210,7 +210,7 @@ public function __construct($rrule = null, $startDate = null, $endDate = null, $
 
         if (is_array($rrule)) {
             $this->loadFromArray($rrule);
-        } else if (!empty($rrule)) {
+        } elseif (!empty($rrule)) {
             $this->loadFromString($rrule);
         }
     }
@@ -286,35 +286,64 @@ public function loadFromString($rrule)
      */
     public function parseString($rrule)
     {
-        if (strpos($rrule, 'DTSTART:') === 0) {
-            $pieces = explode(':', $rrule);
+        //rrule here can be:
+        //1) DTSTART:20200607T120200
+        //2) DTSTART;TZID=UTC:20200607T120200
+        //3) RRULE:FREQ=DAILY;INTERVAL=1
+        //4) FREQ=DAILY;DTSTART;TZID=UTC:20200607T120200;INTERVAL=1
+        //5) FREQ=DAILY;DTSTART:20200607T120200;INTERVAL=1
+
+        //SOLUTION: split by ';':
+        //1) [DTSTART:20200607T120200]
+        //2) [DTSTART, TZID=UTC:20200607T120200]
+        //3) [RRULE:FREQ=DAILY, INTERVAL=1]
+        //4) [FREQ=DAILY, DTSTART, TZID=UTC:20200607T120200, INTERVAL=1]
+        //5) [FREQ=DAILY, DTSTART:20200607T120200, INTERVAL=1]
+
+        $fragments = explode(';', $rrule);
+
+        if (!count($fragments)) {
+            throw new InvalidRRule('RRULE is empty');
+        }
 
-            if (count($pieces) !== 2) {
-                throw new InvalidRRule('DSTART is not valid');
+        $parts  = array();
+        foreach ($fragments as $fragment) {
+            if (strpos($fragment, 'RRULE:') === 0) {
+                $fragment = str_replace('RRULE:', '', $fragment);
             }
 
-            return array('DTSTART' => $pieces[1]);
-        }
 
-        if (strpos($rrule, 'RRULE:') === 0) {
-            $rrule = str_replace('RRULE:', '', $rrule);
-        }
+            if (strpos($fragment, 'DTSTART') === 0) {
+                if ($fragment === 'DTSTART') {
+                    $parts['DTSTART'] = '';//to be replaced by next token
 
-        $pieces = explode(';', $rrule);
-        $parts  = array();
+                    continue;
+                }
 
-        if (!count($pieces)) {
-            throw new InvalidRRule('RRULE is empty');
-        }
+                $p = explode(':', $fragment);
+                if (count($p) !== 2) {
+                    throw new InvalidRRule('DTSTART is not valid');
+                }
+
+                $parts['DTSTART'] = $p[1];
 
-        // Split each piece of the RRULE in to KEY=>VAL
-        foreach ($pieces as $piece) {
-            if (false === strpos($piece, '=')) {
                 continue;
             }
 
-            list($key, $val) = explode('=', $piece);
-            $parts[$key] = $val;
+            if (strpos($fragment, '=')) {
+                list($key, $val) = explode('=', $fragment);
+
+                if ($key === 'TZID') {
+                    $p = explode(':', $val);
+
+                    $parts['TZID'] = $p[0];
+                    $parts['DTSTART'] = $p[1];
+
+                    continue;
+                }
+
+                $parts[$key] = $val;
+            }
         }
 
         return $parts;
@@ -341,11 +370,26 @@ public function loadFromArray($parts)
             $this->setFreq(self::$freqs[$parts['FREQ']]);
         }
 
+        // TZID
+        if (isset($parts['TZID'])) {
+            $this->setTimezone($parts['TZID']);
+        }
+
         // DTSTART
         if (isset($parts['DTSTART'])) {
             $this->isStartDateFromDtstart = true;
-            $date = new \DateTime($parts['DTSTART']);
-            $date = $date->setTimezone(new \DateTimeZone($this->getTimezone()));
+
+            $timezone = new \DateTimeZone($this->getTimezone());
+            $date = null;
+            if (isset($parts['TZID'])) {
+                //DTSTART is datetime in TZID timezone
+                $date = new \DateTime($parts['DTSTART'], $timezone);
+            } else {
+                //DTSTART is UTC, convert to timezone coming from constructor/startDate/default
+                $date = new \DateTime($parts['DTSTART']);
+                $date = $date->setTimezone($timezone);
+            }
+
             $this->setStartDate($date);
         }
 
@@ -474,12 +518,12 @@ public function getString($timezoneType=self::TZ_FLOAT)
                 $date = $d->format($format);
                 $parts[] = "DTSTART;TZID=$tzid:$date";
             } else {
-                $parts[] = 'DTSTART='.$this->getStartDate()->format($format);
+                $parts[] = 'DTSTART:'.$this->getStartDate()->format($format);
             }
         }
 
         // DTEND
-        if ($this->endDate instanceof \DateTime) {
+        if ($this->endDate instanceof \DateTimeInterface) {
             if ($timezoneType === self::TZ_FIXED) {
                 $d = $this->getEndDate();
                 $tzid = $d->getTimezone()->getName();
diff --git a/tests/Recurr/Test/RuleTest.php b/tests/Recurr/Test/RuleTest.php
index 3471f34..0e19155 100644
--- a/tests/Recurr/Test/RuleTest.php
+++ b/tests/Recurr/Test/RuleTest.php
@@ -6,6 +6,7 @@
 use Recurr\DateInclusion;
 use Recurr\Frequency;
 use Recurr\Rule;
+use DateTimeImmutable;
 
 class RuleTest extends \PHPUnit_Framework_TestCase
 {
@@ -17,6 +18,49 @@ public function setUp()
         $this->rule = new Rule;
     }
 
+    public function testCanConvertRruleBackAndForthAndGetSameResult()
+    {
+        $rrules = [
+            "DTSTART:20200607T120200\r\nRRULE:FREQ=DAILY;INTERVAL=1",
+            "DTSTART;TZID=Europe/London:20200607T120200\r\nRRULE:FREQ=DAILY;INTERVAL=1"
+        ];
+
+        foreach ($rrules as $rrule) {
+            $rule = new Rule($rrule);
+            $rruleOne = $rule->getString(Rule::TZ_FIXED);
+
+            $rule2 = new Rule($rruleOne);
+            $rruleTwo = $rule2->getString(Rule::TZ_FIXED);
+
+            $this->assertSame($rruleOne, $rruleTwo);
+        }
+    }
+
+    public function testCanCreateRuleFromStringHavingTzid()
+    {
+        $rule = new Rule("DTSTART;TZID=Europe/London:20200607T120200\r\nRRULE:FREQ=DAILY;INTERVAL=1");
+
+        $this->assertEquals('EUROPE/LONDON', $rule->getTimezone());
+
+        $startDate = $rule->getStartDate();
+        $this->assertSame('2020-06-07 12:02:00', $startDate->format('Y-m-d H:i:s'));
+
+
+        $this->assertSame('EUROPE/LONDON', $startDate->getTimezone()->getName());
+    }
+
+    public function testCanCreateRruleIfEndIsPassedAsDateTimeImmutable()
+    {
+        $begin = new DateTimeImmutable('2012-08-01');
+        $end = new DateTimeImmutable('2012-08-31');
+        $xmas = new DateTimeImmutable('2012-12-25');
+
+        $rule = new Rule('FREQ=WEEKLY;COUNT=5', $begin, $end);
+        $string = $rule->getString();
+
+        $this->assertEquals('FREQ=WEEKLY;COUNT=5;DTEND=20120831T000000', $string);
+    }
+
     public function testConstructAcceptableStartDate()
     {
         $this->rule = new Rule(null, null);
@@ -282,7 +326,7 @@ public function testLoadFromStringWithDtstart()
         $defaultTimezone = date_default_timezone_get();
         date_default_timezone_set('America/Chicago');
 
-        $string = 'FREQ=MONTHLY;DTSTART=20140222T073000';
+        $string = 'FREQ=MONTHLY;DTSTART:20140222T073000';
 
         $this->rule->setTimezone('America/Los_Angeles');
         $this->rule->loadFromString($string);
@@ -363,7 +407,7 @@ public function testGetStringWithUTC()
 
     public function testGetStringWithDtstart()
     {
-        $string = 'FREQ=MONTHLY;DTSTART=20140210T163045;INTERVAL=1;WKST=MO';
+        $string = 'FREQ=MONTHLY;DTSTART:20140210T163045;INTERVAL=1;WKST=MO';
 
         $this->rule->loadFromString($string);
 
@@ -424,7 +468,7 @@ public function testSetStartDateAffectsStringOutput()
         $this->assertEquals('FREQ=MONTHLY;COUNT=2', $this->rule->getString());
 
         $this->rule->setStartDate(new \DateTime('2015-12-10'), true);
-        $this->assertEquals('FREQ=MONTHLY;COUNT=2;DTSTART=20151210T000000', $this->rule->getString());
+        $this->assertEquals('FREQ=MONTHLY;COUNT=2;DTSTART:20151210T000000', $this->rule->getString());
 
         $this->rule->setStartDate(new \DateTime('2015-12-10'), false);
         $this->assertEquals('FREQ=MONTHLY;COUNT=2', $this->rule->getString());