Make so date format can manually be changed from system date format setting

[JSpenced]

I use USA settings as default, but prefer european date format, so I change this in the settings on Mojave (just upgraded from El Capitan). But it takes the default system setting and not the updated setting. I would prefer if this was user changeable if you want it to be Year-Month-Day or Day-Month-Year.

When it is Day-Month-Year, mostly I change the day so it makes it a lot easier everytime I want to change a due date or threshold.