日期范围内的Gnuplot调色板

Question

是否可以使用日期作为范围来定义调色板？

我没有成功尝试过的是：

set title "Running Stats"
set size ratio square
set key off

set xrange [5:45]
set xlabel "Distance"
set xtics 0,5,45

set yrange [3.5:7.5]
set ylabel "Pace"
set ytics nomirror

set timefmt '%Y-%m-%d'
set cbrange ["2018-01-01":"2019-01-01"]
set palette defined ("2018-01-01" 'red', "2019-01-01" 'green')

set style data points
plot data using 2:3:1 linecolor palette lw 1 pt 7