Gnuplot, problems with dates on the x-axis - date

Question

I have (for me) a strange problem with the date on the x-axis.
I use the (imo) linux time in the first column like;
1385856000,1.69,0,10.33,0,1.69,10.33,-8.64,12.14,3.5
1385942400,0,0.94,3.33,8.51,0.94,11.84,-10.9,13.7,2.8
1386028800,0,0.51,4.96,8.65,0.51,13.61,-13.1,15.8,2.7
1386115200,0,0.01,3.42,6.49,0.01,9.91,-9.9,10.6,0.7
V
V
V
1388361600,0,0.63,4.21,7.65,0.63,11.86,-11.23,13.93,2.7
1388448000,0,0.18,4.47,8.29,0.18,12.76,-12.58,14.48,1.9
In this case december 2013 with 31 days. But the line begins with 30 (november?).
For now a draw a rectangle over de "30" but ofcourse thats not the way.
This is my script;
maand = "Dec"
jaar = "2013"
file = maand.jaar.'.txt'
set output maand.jaar.".png"
set datafile separator ","
set linestyle 1 lt 1 lc rgb "black"
set linestyle 2 lt 1 lc rgb "red"
set bmargin 2.2 # witruimte onder grafiek
set label font "arial, 7" # grootte font tbv labels in het grafiek
set boxwidth 0.8 relative
set terminal pngcairo truecolor enhanced size 1200, 500 background rgb "#FFF5F5"
stats file using 0 nooutput ; dagen = STATS_records
stats file using 10 nooutput ; zon = value(int(STATS_sum*1000))
stats file using 9 nooutput ; gebruikt = value(int(STATS_sum*1000))
afgenomen = gebruikt-zon
set timefmt "%s" ; fmt = "%s"
stats file using (strptime(fmt, stringcolumn(1))) every ::1::1 nooutput
maand = strftime("%B", STATS_max) ; jaar = strftime("%Y", STATS_max) ; datum = maand." ".jaar
set title 'Energie stromen '.datum font "arial bold, 14"
set xdata time ; set timefmt "%s" ; set format x "%d" # dit is de opmaak zoals je hem gaat zien
set xtics 86400 font "arial,12" offset -1.35,0.5
set mxtics 1
set grid ls 1 lc rgb "#dddddd"
set ytics font "arial, 12" offset 0.5,0
set ylabel "V e r m o g e n in kW" offset 3,1 font "helvetica, 12"
unset key
set key below left samplen 2
set key maxrows 1 # aantal regels onder het grafiek (met Watt/uur erin)
set style fill solid 1 border 0.5 # was transparent solid 0.5 border 0.5
set style rectangle fc linestyle 1 fs solid 0.5 noborder
set object rectangle front fillcolor rgb "#FFF5F5"
set object 2 rect from graph -.48, graph -1.5 to graph -0.004, graph 0.02 fc rgb "#FFF5F5"
plot file u ($1-43200):10 w boxes lc rgb "#00ff00" title "Deze maand zon: ".(zon/1000)." kW",\
file u ($1-43200):10:(sprintf("%2.1f",$10)) w labels offset 0.0,0.4 font "arial, 10" notitle,\
file u ($1-43200):(-1*$9) w boxes lc rgb "#ff0000" title "&{2}Verbruik: ".(gebruikt/1000)." kW",\
file u ($1-43200):(-1*$9):(sprintf("%2.1f",$9)) w labels offset 0,-0.4 font "arial, 10" notitle
Has some one a clou?

Answer 1

The 30 comes from november and the way you shift the xticlabels.
I think, the best way to have the labels below the boxes, but the tics and the grid lines between the boxes is the following:
Scale the major tics to 0
Add one minor xtic and draw the grid lines only for the minor xtics
Do not expand the automatic xrange to the next major tic (set autoscale xfix)
Plot the boxes at their actual time position (plot file u 1:... instead of plot file u ($1-43200):...)
...
set xtics 86400 font "arial,12" scale 0, 1
set mxtics 2
set grid mxtics ytics ls 1 lc rgb "#dddddd"
set autoscale xfix
...
plot file u 1:10 w boxes lc rgb "#00ff00"
...
With these modifications, your exemplary data and version 4.6.3 I get
BTW: You can compress your three stats calls to a single one:
stats file using 9:10 nooutput
dagen = STATS_records
zon = int(STATS_sum_y*1000)
gebruikt = int(STATS_sum_x*1000)