Why is LocalDateTime used rather than Instant for FIX UTCTimestamps?

[abissell]

I tried figuring this out for myself from documentation, code, and discussion on Github but couldn't seem to find an answer. I was wondering, why is LocalDateTime used for FIX UTCTimestamp fields like SendingTime? From my cursory reading about the two different types, LocalDateTime is not intended to carry any timezone information with it, while Instant represents a moment on the UTC timeline, which seems to correspond more closely to the FIX spec definition of these fields.

Appreciate any insights you can offer, thanks!

[abissell]

BTW I hope this doesn't come across as language lawyering or anything, the reason I ask is I'm writing a library to serve as an intermediate layer between Quickfix/J and other Java FIX implementations, and just want to pick the best data type for the UTC timestamp fields. Thanks

[chrjohn]

No problem, it is a good question indeed. :)
I shortly thought about it and couldn't find a good reason. I'll give it another thought after the weekend. But it'll probably turn out as ignorance.

[chrjohn]

This was some years ago, maybe I thought LocalTime with UtcTimeOnly fields vs LocalDateTime with UtcTimestamp field was a good idea.
However, please feel free to open a corresponding issue or PR. Thank you. :)