[Bug]Generator using fromUnixTimeSeconds for unixTimestamp with int64

[yifan-zhou922]

Describe the issue or request
When defining the createTime as @encode(DateTimeKnownEncoding.unixTimestamp, int64) in TypeSpec, the generator uses FromUnixTimeSeconds.
However, in the service use case, the createTime is in milliseconds. So an error for out-of-range is raised.

Here is the sample for createTime/updateTime.

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how these changes might work for multiple services.

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[ArcturusZhang]

We are calling the wrong method all day along:

autorest.csharp/src/AutoRest.CSharp/Common/Output/Builders/JsonSerializationMethodsBuilder.cs

Line 1154 in fa9971f

? DateTimeOffsetExpression.FromUnixTimeSeconds(element.GetInt64())

But all the information I could find, such as:

• https://www.unixtimestamp.com/
• https://en.wikipedia.org/wiki/Unix_time
  says the unix timestamp is seconds instead of milliseconds.

The typespec doc here never says it is milliseconds or seconds, it looks like milliseconds

[mikeharder]

I'm pretty sure it is milliseconds. TypeSpec is heavily influenced by JavaScript, and the JS Date object uses milliseconds since the epoch.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date

[mikeharder]

@ArcturusZhang: If this is a simple fix to call FromUnixTimeMilliseconds() instead of FromUnixTimeSeconds(), could this be fixed quickly, so the spec doesn't need to apply a workaround?

[johanste]

@bterlson, this was intended as seconds, not milliseconds, right?

[mikeharder]

@johanste, @bterlson: Best issue for discussion is microsoft/typespec#2887

[mikeharder]

@ArcturusZhang: Per discussion in microsoft/typespec#2887, it seems that the intention of DateTimeKnownEncoding.unixTimestamp in TypeSpec was seconds since epoch, so autorest.csharp is correct.

[ArcturusZhang]

@ArcturusZhang: Per discussion in microsoft/typespec#2887, it seems that the intention of DateTimeKnownEncoding.unixTimestamp in TypeSpec was seconds since epoch, so autorest.csharp is correct.

So I bring this up because of being afraid there would be debates like this because it is really unclear on typespec documents, and different person with different background would have different comprehension on the work "unix timestamp". My first thought is that this is "seconds".

Service teams (slash typespec authors) might also have the same confusion depending on their background - therefore this is really ambiguous.
Please make sure we clarify that enough
Currently dotnet generator will not change since it is the correct intention. If we do need a change, it is really simple, just replace the method we are using from DateTimeOffset.FromUnixSeconds to FromUnixMilliseconds.

[ArcturusZhang]

Close this because our current behavior is correct

[mikeharder]

@ArcturusZhang: Per discussion in microsoft/typespec#2887, it seems that the intention of DateTimeKnownEncoding.unixTimestamp in TypeSpec was seconds since epoch, so autorest.csharp is correct.

So I bring this up because of being afraid there would be debates like this because it is really unclear on typespec documents, and different person with different background would have different comprehension on the work "unix timestamp". My first thought is that this is "seconds".

Service teams (slash typespec authors) might also have the same confusion depending on their background - therefore this is really ambiguous. Please make sure we clarify that enough Currently dotnet generator will not change since it is the correct intention. If we do need a change, it is really simple, just replace the method we are using from DateTimeOffset.FromUnixSeconds to FromUnixMilliseconds.

@ArcturusZhang: If you have any more feedback not already captured microsoft/typespec#2887, please add it to that issue.