Factored-out "dates" derivation in XAxisLabelStyle(), because:
Factored-out "dates" derivation in XAxisLabelStyle(), because:

it can be passed in from callers.
thongsav-usgs/repgen,zmoore-usgs/repgen,thongsav-usgs/repgen,USGS-R/repgen,lindsaycarr/repgen,dpattermann-usgs/repgen,lindsaycarr/repgen,mhines-usgs/repgen,mhines-usgs/repgen,USGS-R/repgen,zmoore-usgs/repgen,zmoore-usgs/repgen,USGS-R/repgen,dpattermann-usgs/repgen,mhines-usgs/repgen,thongsav-usgs/repgen,lindsaycarr/repgen,dpattermann-usgs/repgen