This command sets the datatype on the x axis to time/date. A similar command does the same thing for each of the other axes.
Syntax:
set xdata {time}
show xdata
The same syntax applies to ydata, zdata, x2data and y2data.
The time option signals that the datatype is indeed time/date. If the option is not specified, the datatype reverts to normal.
See set timefmt to tell gnuplot how to read date or time data. The time/date is converted to seconds from start of the century. There is currently only one timefmt, which implies that all the time/date columns must confirm to this format. Specification of ranges should be supplied as quoted strings according to this format to avoid interpretation of the time/date as an expression.
The function 'strftime' (type "man strftime" on unix to look it up) is used to print tic-mark labels. gnuplot tries to figure out a reasonable format for this unless the set format x "string" has supplied something that does not look like a decimal format (more than one '%' or neither %f nor %g).
See also Time/date for more information.