Well, it always helps to have empathy towards the end-user in order to achieve as much ergonomic and intuitive programs, but back to your case, the programmer in charge of redacting the database transaction layer is supposed to make sure that the date is stored using a time-stamp, whereas the UI programmer should take care of accordingly parsing this time-stamp on an end-user localization basis so that the end-user can for example always remotely generate a consistent receipt whatever his location. But yes, both programmers can definitely be the same person. Presenting information to the world in various notations or languages require more UI efforts than using more standardized schemes, but have its charms. In all cases, if the data is presented ambiguously, then the project is an epic failure (!?), with data dumped to the end-user becoming inconsistent so unusable, but in theory and back to your initial question, inside a project with respective road-maps for several programmers, it would be the UI programmer's job to properly dump / format data that have been consistently stored.

Kaveh Rassoulzadegan