Why not to use Java default ISO_OFFSET_DATE_TIME in DateTimeScalar

[sadv1r]

I needed to fix ZoneId in my dates from server and found something that I don't see a reason for, can some one help?

In DateTimeScalar

Is there any reason why this code is used:

private static DateTimeFormatter getCustomDateTimeFormatter() {
        return new DateTimeFormatterBuilder()
                .parseCaseInsensitive()
                .append(ISO_LOCAL_DATE)
                .appendLiteral('T')
                .appendValue(HOUR_OF_DAY, 2)
                .appendLiteral(':')
                .appendValue(MINUTE_OF_HOUR, 2)
                .appendLiteral(':')
                .appendValue(SECOND_OF_MINUTE, 2)
                .appendFraction(NANO_OF_SECOND, 3, 3, true)
                .appendOffset("+HH:MM", "Z")
                .toFormatter();
}

and not something like this:

private static DateTimeFormatter getCustomDateTimeFormatter() {
        return DateTimeFormatter.ISO_OFFSET_DATE_TIME;
}

[dondonz]

Good question!

There is a story behind this. DateTime has been implemented differently across different languages, because the original RFC 3339 wasn't specific enough. At work we had a problem where the number of digits used to express nanoseconds was different in two implementations. It was a subtle difference, but it can have an impact.

After this happened we created a way to standardise GraphQL Scalars across implementations. Here's a blog explaining more background behind the GraphQL Scalars initiative https://graphql.org/blog/2023-01-14-graphql-scalars/

And you can see the DateTime spec here: https://scalars.graphql.org/andimarek/date-time.html. The crucial part of this spec is requiring always three digits for nanoseconds.

So to answer your question, we have a verbose way to express DateTime so we are certain to conform to this DateTime specification.

[dondonz]

In the code, we have linked to the DateTime specification page via the @specifiedBy built-in directive

[sadv1r]

Oh @dondonz thank you so much for such detailed explanation, now it's really makes sense for me!😊