Selecting the option to have minor interval marks drawn also draws marks at the
major intervals.  However, selecting the option to have minor grid lines does
not also draw grid lines at the major intervals.

It would be better if minor interval marks and grid lines were consistent,
preferably, by not drawing the minor interval marks at the major intervals.

The issue is usually not noticed because when the minor interval marks option is
selected, usually the major interval marks option is also selected, and the
major interval marks overdraw the minor interval marks.

Correcting this issue would allow an X-axis representing years to be drawn like

     |        |        |        |
        2005     2006     2007

where the year labels are at major intervals and the boundaries between year are
at minor intervals.