diff --git a/phpseclib/File/ASN1.php b/phpseclib/File/ASN1.php
index 53ac6ff2..1a8c02d9 100644
--- a/phpseclib/File/ASN1.php
+++ b/phpseclib/File/ASN1.php
@@ -27,6 +27,8 @@ use ParagonIE\ConstantTime\Base64;
 use phpseclib\File\ASN1\Element;
 use phpseclib\Math\BigInteger;
 use phpseclib\Common\Functions\Strings;
+use DateTime;
+use DateTimeZone;
 
 /**
  * Pure-PHP ASN.1 Parser
@@ -739,7 +741,7 @@ abstract class ASN1
                 if (isset($mapping['implicit'])) {
                     $decoded['content'] = self::decodeTime($decoded['content'], $decoded['type']);
                 }
-                return @date(self::$format, $decoded['content']);
+                return $decoded['content'] ? $decoded['content']->format(self::$format) : false;
             case self::TYPE_BIT_STRING:
                 if (isset($mapping['mapping'])) {
                     $offset = ord($decoded['content'][0]);
@@ -989,7 +991,8 @@ abstract class ASN1
             case self::TYPE_GENERALIZED_TIME:
                 $format = $mapping['type'] == self::TYPE_UTC_TIME ? 'y' : 'Y';
                 $format.= 'mdHis';
-                $value = @gmdate($format, strtotime($source)) . 'Z';
+                $date = new DateTime($source, new DateTimeZone('GMT'));
+                $value = $date->format($format) . 'Z';
                 break;
             case self::TYPE_BIT_STRING:
                 if (isset($mapping['mapping'])) {
@@ -1151,33 +1154,32 @@ abstract class ASN1
            http://tools.ietf.org/html/rfc5280#section-4.1.2.5.2
            http://www.obj-sys.com/asn1tutorial/node14.html */
 
-        $pattern = $tag == self::TYPE_UTC_TIME ?
-            '#^(..)(..)(..)(..)(..)(..)?(.*)$#' :
-            '#(....)(..)(..)(..)(..)(..).*([Z+-].*)$#';
-
-        preg_match($pattern, $content, $matches);
-
-        list(, $year, $month, $day, $hour, $minute, $second, $timezone) = $matches;
+        $format = 'YmdHis';
 
         if ($tag == self::TYPE_UTC_TIME) {
-            $year = $year >= 50 ? "19$year" : "20$year";
-        }
-
-        if ($timezone == 'Z') {
-            $mktime = 'gmmktime';
-            $timezone = 0;
-        } elseif (preg_match('#([+-])(\d\d)(\d\d)#', $timezone, $matches)) {
-            $mktime = 'gmmktime';
-            $timezone = 60 * $matches[3] + 3600 * $matches[2];
-            if ($matches[1] == '-') {
-                $timezone = -$timezone;
+            // https://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf#page=28 says "the seconds
+            // element shall always be present" but none-the-less I've seen X509 certs where it isn't and if the
+            // browsers parse it phpseclib ought to too
+            if (preg_match('#^(\d{10})(Z|[+-]\d{4})$#', $content, $matches)) {
+                $content = $matches[1] . '00' . $matches[2];
             }
-        } else {
-            $mktime = 'mktime';
-            $timezone = 0;
+            $prefix = substr($content, 0, 2) >= 50 ? '19' : '20';
+            $content = $prefix . $content;
+        } elseif (strpos($content, '.') !== false) {
+            $format.= '.u';
         }
 
-        return @$mktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year) + $timezone;
+        if ($content[strlen($content) - 1] == 'Z') {
+            $content = substr($content, 0, -1) . '+0000';
+        }
+
+        if (strpos($content, '-') !== false || strpos($content, '+') !== false) {
+            $format.= 'O';
+        }
+
+        // error supression isn't necessary as of PHP 7.0:
+        // http://php.net/manual/en/migration70.other-changes.php
+        return @DateTime::createFromFormat($format, $content);
     }
 
     /**
diff --git a/phpseclib/File/X509.php b/phpseclib/File/X509.php
index 51161b21..619527cb 100644
--- a/phpseclib/File/X509.php
+++ b/phpseclib/File/X509.php
@@ -35,7 +35,8 @@ use phpseclib\Exception\UnsupportedAlgorithmException;
 use phpseclib\File\ASN1\Element;
 use phpseclib\Math\BigInteger;
 use phpseclib\File\ASN1\Maps;
-
+use DateTime;
+use DateTimeZone;
 
 /**
  * Pure-PHP X.509 Parser
@@ -1061,7 +1062,7 @@ class X509
         }
 
         if (!isset($date)) {
-            $date = time();
+            $date = new DateTime($date, new DateTimeZone(date_default_timezone_get()));
         }
 
         $notBefore = $this->currentCert['tbsCertificate']['validity']['notBefore'];
@@ -1071,8 +1072,8 @@ class X509
         $notAfter = isset($notAfter['generalTime']) ? $notAfter['generalTime'] : $notAfter['utcTime'];
 
         switch (true) {
-            case $date < @strtotime($notBefore):
-            case $date > @strtotime($notAfter):
+            case $date < new DateTime($notBefore, new DateTimeZone(@date_default_timezone_get())):
+            case $date > new DateTime($notAfter, new DateTimeZone(@date_default_timezone_get())):
                 return false;
         }
 
@@ -2290,7 +2291,11 @@ class X509
      */
     private function timeField($date)
     {
-        $year = @gmdate("Y", @strtotime($date)); // the same way ASN1.php parses this
+        if ($date instanceof Element) {
+            return $date;
+        }
+        $dateObj = new DateTime($date, new DateTimeZone('GMT'));
+        $year = $dateObj->format('Y'); // the same way ASN1.php parses this
         if ($year < 2050) {
             return ['utcTime' => $date];
         } else {
@@ -2355,8 +2360,12 @@ class X509
                 return false;
             }
 
-            $startDate = !empty($this->startDate) ? $this->startDate : @date('D, d M Y H:i:s O');
-            $endDate = !empty($this->endDate) ? $this->endDate : @date('D, d M Y H:i:s O', strtotime('+1 year'));
+            $startDate = new DateTime('now', new DateTimeZone(@date_default_timezone_get()));
+            $startDate = !empty($this->startDate) ? $this->startDate : $startDate->format('D, d M Y H:i:s O');
+
+            $endDate = new DateTime('+1 year', new DateTimeZone(@date_default_timezone_get()));
+            $endDate = !empty($this->endDate) ? $this->endDate : $endDate->format('D, d M Y H:i:s O');
+
             /* "The serial number MUST be a positive integer"
                "Conforming CAs MUST NOT use serialNumber values longer than 20 octets."
                 -- https://tools.ietf.org/html/rfc5280#section-4.1.2.2
@@ -2624,7 +2633,9 @@ class X509
 
         $currentCert = isset($this->currentCert) ? $this->currentCert : null;
         $signatureSubject = isset($this->signatureSubject) ? $this->signatureSubject : null;
-        $thisUpdate = !empty($this->startDate) ? $this->startDate : @date('D, d M Y H:i:s O');
+
+        $thisUpdate = new DateTime('now', new DateTimeZone(@date_default_timezone_get()));
+        $thisUpdate = !empty($this->startDate) ? $this->startDate : $thisUpdate->format('D, d M Y H:i:s O');
 
         if (isset($crl->currentCert) && is_array($crl->currentCert) && isset($crl->currentCert['tbsCertList'])) {
             $this->currentCert = $crl->currentCert;
@@ -2777,7 +2788,11 @@ class X509
      */
     public function setStartDate($date)
     {
-        $this->startDate = @date('D, d M Y H:i:s O', @strtotime($date));
+        if (!is_object($date) || !is_a($date, 'DateTime')) {
+            $date = new DateTime($date);
+        }
+
+        $this->startDate = $date->format('D, d M Y H:i:s O');
     }
 
     /**
@@ -2800,7 +2815,11 @@ class X509
             $temp = chr(ASN1::TYPE_GENERALIZED_TIME) . ASN1::encodeLength(strlen($temp)) . $temp;
             $this->endDate = new Element($temp);
         } else {
-            $this->endDate = @date('D, d M Y H:i:s O', @strtotime($date));
+            if (!is_object($date) || !is_a($date, 'DateTime')) {
+                $date = new DateTime($date);
+            }
+
+            $this->endDate = $date->format('D, d M Y H:i:s O');
         }
     }
 
@@ -3530,8 +3549,9 @@ class X509
         }
 
         $i = count($rclist);
+        $revocationDate = new DateTime('now', new DateTimeZone(@date_default_timezone_get()));
         $rclist[] = ['userCertificate' => $serial,
-                          'revocationDate'  => $this->timeField(@date('D, d M Y H:i:s O'))];
+                          'revocationDate'  => $this->timeField($revocationDate->format('D, d M Y H:i:s O'))];
         return $i;
     }