Date column has issues with dates before 1AD

I am using a board for history research. I use the date column for recording birth dates of various historical figures. I can select a BCE (before common era) date from the little calendar popup, but as soon as the field populates, it switches to an CE (common era) year. For example, if I select January 1, 640 BCE from the calendar, it populates the field as January 1, 640 CE… a difference of over a millennium!