startTime

The time stamp indicating the earliest data to be returned.

The value specified is inclusive; results include data points with the specified time stamp.

CloudWatch rounds the specified time stamp as follows:

• Start time less than 15 days ago - Round down to the nearest whole minute. For example, 12:32:34 is rounded down to 12:32:00.

• Start time between 15 and 63 days ago - Round down to the nearest 5-minute clock interval. For example, 12:32:34 is rounded down to 12:30:00.

• Start time greater than 63 days ago - Round down to the nearest 1-hour clock interval. For example, 12:32:34 is rounded down to 12:00:00.

If you set Period to 5, 10, 20, or 30, the start time of your request is rounded down to the nearest time that corresponds to even 5-, 10-, 20-, or 30-second divisions of a minute. For example, if you make a query at (HH:mm:ss) 01:05:23 for the previous 10-second period, the start time of your request is rounded down and you receive data from 01:05:10 to 01:05:20. If you make a query at 15:07:17 for the previous 5 minutes of data, using a period of 5 seconds, you receive data timestamped between 15:02:15 and 15:07:15.

For better performance, specify StartTime and EndTime values that align with the value of the metric's Period and sync up with the beginning and end of an hour. For example, if the Period of a metric is 5 minutes, specifying 12:05 or 12:30 as StartTime can get a faster response from CloudWatch than setting 12:07 or 12:29 as the StartTime.