When I work in history I don’t use the built-in date field as I find it too inconvenient. Too many of the dates I use are either “incomplete”, or sometimes I need to use periods of time like January to March, or 1815 to 1830. So basically I roll my own. I define a year field, a month field, and so forth. I even have a modifier field which has items like “before” or “circa” and so on. This gives me a lot of flexibility.