About the Time Stamp
The time stamp (or expiration time) you use in the request must be a
object, with the complete date plus hours, minutes, and seconds (for more information, see
http://www.w3.org/TR/xmlschema-2/#dateTime). For example: 2007-01-31T23:59:59Z.
Although it's not required, we recommend you provide the time stamp in the Coordinated Universal
Time (Greenwich Mean Time) time zone.
If you specify a time stamp (instead of an expiration time), the request automatically expires 15 minutes after the time stamp (in other words, AWS does not process a request if the request time stamp is more than 15 minutes earlier than the current time on AWS servers). Make sure your server's time is set correctly.
If you're using .NET you must not send overly specific time stamps, due to different
interpretations of how extra time precision should be dropped. To avoid overly specific time
stamps, manually construct
dateTime objects with no more than millisecond