Timestamp format

[Nugine]

AWS glossary says timestamp (date/time) is in ISO8601 format. But Smithy specification says timestamp (date-time) is in RFC3339 format. The difference may be whether to accept timestamp strings like 1970-08-06T06:06:18.1Z.
Which one is correct?

Related:

• java.time.format.DateTimeParseException: Text '2023-02-02T18:23:28.9Z' could not be parsed at index 19 minio/minio-java#1419

[jdisanti]

The ISO8601 spec is quite large and includes a lot more date formats than RFC3339. This website illustrates those differences. Of note: ISO8601 specifies durations (e.g., P3Y6M4DT12H30M5S) as well as timestamps, and the Smithy timestamp shape does not support durations. Thus, the Smithy spec uses RFC3339 to be more clear about what is actually supported.

However, from what you linked, it looks like the important difference is the precision of the sub-second fraction. RFC3339 calls for time-secfrac = "." 1*DIGIT in its ABNF, which means 1 or more digits. So technically any number of digits after . are valid. I am not familiar with what is allowed for ISO8601 on the sub-second fraction, but I suspect it's the same.

Edit: To answer, "what is correct," SDKs based on Smithy use the Smithy spec as what is correct for timestamps. Older SDKs not based on Smithy might be more lenient on what they accept and will remain that way for backwards compatibility.