Quite sure, or at least hoping that it is an easy configuration issue, but for now I have not been able to figure out where to change this, I've just found how to change the date input format (which I do not want to change)
In all date fields, comments and such, JIRA is now showing
In X {days|minutes}I would rather have it to show the actual date/time value since there are times that it might lead to confusion and also when requesting a change the time to apply the change is as important as just the date.