Ability to use calendar dates on the x-axis instead of JD

[stewi2]

It would be great to be able to plot calendar dates ion the X-axis instead of JD. This would be very useful when presenting plots to an audience that isn't familiar with JD.

This is basically this issue, but the corresponding Github issue #82 was somehow closed as duplicate of #384, which is related but not the same.

[dbenn]

Thanks @stewi2 for raising this. #82 described a mixture of work ("load from AID and plots") whereas the title of this issue is much more clear.