diff --git a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
index 885de682255..58200ac713d 100644
--- a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
@@ -306,7 +306,15 @@ class ObjectSerializer
             // be interpreted as a missing field/value. Let's handle
             // this graceful.
             if (!empty($data)) {
-                return new \DateTime($data);
+                try {
+                    return new \DateTime($data);
+                } catch (\Exception $exception) {
+                    // Some API's return a date-time with too high nanosecond
+                    // precision for php's DateTime to handle. This conversion
+                    // (string -> unix timestamp -> DateTime) is a workaround
+                    // for the problem.
+                    return (new \DateTime())->setTimestamp(strtotime($data));
+                }
             } else {
                 return null;
             }
diff --git a/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php b/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
index e64b4cab315..9aaec99a557 100644
--- a/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
+++ b/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
@@ -316,7 +316,15 @@ class ObjectSerializer
             // be interpreted as a missing field/value. Let's handle
             // this graceful.
             if (!empty($data)) {
-                return new \DateTime($data);
+                try {
+                    return new \DateTime($data);
+                } catch (\Exception $exception) {
+                    // Some API's return a date-time with too high nanosecond
+                    // precision for php's DateTime to handle. This conversion
+                    // (string -> unix timestamp -> DateTime) is a workaround
+                    // for the problem.
+                    return (new \DateTime())->setTimestamp(strtotime($data));
+                }
             } else {
                 return null;
             }