title: Amazon DynamoDB InvalidSignatureException
body: <p>From this code I'm getting the error below</p>
  
  <pre><code>require "vendor/autoload.php";
  use Aws\Common\Aws;
  use Aws\DynamoDb\DynamoDbClient;
  use Aws\DynamoDb\Enum\ComparisonOperator;
  use Aws\DynamoDb\Enum\KeyType;
  use Aws\DynamoDb\Enum\Type;
  
  $aws = Aws::factory(array(
  'key'    =&gt; '[clipped]',
  'secret' =&gt; '[clipped]',
  'region' =&gt; Region::US_WEST_1
  ));
  
  $client = $aws-&gt;get("dynamodb");
  $tableName = "ExampleTable";
  
  $result = $client-&gt;createTable(array(
      "TableName" =&gt; $tableName,
      "AttributeDefinitions" =&gt; array(
          array(
             "AttributeName" =&gt; "Id",
             "AttributeType" =&gt; Type::NUMBER
          )
       ),
       "KeySchema" =&gt; array(
          array(
             "AttributeName" =&gt; "Id",
             "KeyType" =&gt; KeyType::HASH
          )
      ),
      "ProvisionedThroughput" =&gt; array(
          "ReadCapacityUnits"    =&gt; 5,
          "WriteCapacityUnits" =&gt; 6
      )
  ));
  
  print_r($result-&gt;getPath('TableDescription'));
  </code></pre>
  
  <p>I'm getting the following error when trying to add a table into AWS's DynamoDB.</p>
  
  <pre><code>PHP Fatal error:  Uncaught Aws\\DynamoDb\\Exception\\DynamoDbException: AWS Error Code:
  InvalidSignatureException, 
  Status Code: 400, 
  AWS Request ID: [clipped], 
  AWS Error Type: client, 
  AWS Error Message: Signature expired: 20130818T021159Z is now earlier than  
  20130818T021432Z (20130818T022932Z - 15 min.), 
  User-Agent: aws-sdk-php2/2.4.3 Guzzle/3.7.2 curl/7.21.6 PHP/5.3.6-13ubuntu3.9\n  thrown in
  /var/www/vendor/aws/aws-sdk-php/src/Aws/Common/Exception/NamespaceExceptionFactory.php on
  line 91
  </code></pre>
  
  <p>So far I've:</p>
  
  <ul>
  <li>Checked to see if Authentication Key and Secret Key were correct, they were.</li>
  <li>Updated cURL</li>
  <li>When I put false authentication permissions in, the error didn't change.</li>
  </ul>