Documentation Issue: Aws::CloudWatch::Model::MetricDatum does not specify the units of the "timestamp" field

The "timestamp" field of a CloudWatch MetricDatum is used to tag a piece of data with the time at which it occurred. The AWS SDK CPP specifies this timestamp field as a double type, but does not indicate what the double actually represents.

Here is the current documentation from the MetricDatum.h file:

/*
     <p> The time stamp used for the metric. If not specified, the default value is set to the time the metric data was received. Amazon CloudWatch uses Coordinated Universal Time (UTC) when returning time stamps, which do not accommodate seasonal adjustments such as daylight savings time. For more information, see <a href="http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/cloudwatch_concepts.html#about_timestamp">Time stamps</a> in the <i>Amazon CloudWatch Developer Guide</i>. </p>
    */
    inline double GetTimestamp() const{ return m_timestamp; }

    /*
     <p> The time stamp used for the metric. If not specified, the default value is set to the time the metric data was received. Amazon CloudWatch uses Coordinated Universal Time (UTC) when returning time stamps, which do not accommodate seasonal adjustments such as daylight savings time. For more information, see <a href="http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/cloudwatch_concepts.html#about_timestamp">Time stamps</a> in the <i>Amazon CloudWatch Developer Guide</i>. </p>
    */
    inline void SetTimestamp(double value) { m_timestampHasBeenSet = true; m_timestamp = value; }

    /*
     <p> The time stamp used for the metric. If not specified, the default value is set to the time the metric data was received. Amazon CloudWatch uses Coordinated Universal Time (UTC) when returning time stamps, which do not accommodate seasonal adjustments such as daylight savings time. For more information, see <a href="http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/cloudwatch_concepts.html#about_timestamp">Time stamps</a> in the <i>Amazon CloudWatch Developer Guide</i>. </p>
    */
    inline MetricDatum& WithTimestamp(double value) { SetTimestamp(value); return *this;}

Should the double be interpreted as milliseconds since the 1970 epoch? Or seconds? Or something else entirely? CloudWatch itself expects an 8601 ISO formatted timestamp, so it is not entirely clear how this double field maps onto that timestamp.

Alternately, would it make sense to have a variant of the setters for timestamp that takes in a std::chrono::time_point (http://en.cppreference.com/w/cpp/chrono/time_point) object?

[JonathanHenson]

double in timestamp is Amazon's timestamp format. It is in seconds.milliseconds

[JonathanHenson]

seconds.milliseconds from epoch

Would it be possible to add that information to the documentation comments for the functions I listed above? That's where I went to try to figure it out originally.

[JonathanHenson]

This documentation comes directly from the service docs. We can talk to the owners of that documentation and work on getting it updated. Thanks for the callout!

[JonathanHenson]

We've reworked date timestamp fields to make this easier to work with and remove the need for extensive documentation. Have a look at aws-cpp-sdk-core/include/aws/core/utils/DateTime.h for more info and reopen if you still have issues.