The set xmtics command converts the x-axis tic marks to months of the
year where 1=Jan and 12=Dec. Overflows are converted modulo 12 to months.
The tics are returned to their default labels by unset xmtics. Similar
commands perform the same duties for the other axes.
The same syntax applies to x2mtics, ymtics, y2mtics, zmtics and
See also the set format (p. ) command.