I think developers need to clearly understand this and then make reasonable (ideally also visible) choices for the reference frame used in the frontend. For ex

I think developers need to clearly understand this and then make reasonable (ideally also visible) choices for the reference frame used in the frontend. For example the last application I worked on used UTC everywhere in the backend, database, APIs etc and stored a timezone configuration per account. The frontend used that timezone when displaying any date/time and also for parsing user date inputs. With a few places having a timezone drop down next to an input in places where it made business sense for the user to mean an explicit timezone.