First of all, we will specify that the x axis will display time information.
We will now define the format of the input data with the
Gnuplot use a standard way to describe date and time (try
help timefmt to have
more information). For us, it is a timestamp so we will use the
"%s" time format.
We also want to format the output time format (the one that will be displayed on
the graphic) with the following:
%d for the day
%m for the month
%H for the hour
set format x "%d/%m %Hh";
Finally, we need to define the interval between to ticks in order to displayed
ticks only on midnight and midday. For this, we need to make a small calculus.
The timestamp is expressed in seconds. The interval we are taking to is 12
hours. So we need to express 12 hours in seconds which is 43200.