Datafile: time_data.txt

Using the code provided in “Tutorial 02. Time-based data when plotting in gnuplot”, use the histogram style, and format the xtic labels using strftime and timecolumn.

set timefmt "%H:%S"
set style fill solid 0.6 border -1
set style data histogram
set style histogram clustered gap 1 plot 'data.dat' using 2:xtic(strftime('%H', timecolumn(1))), \ '' using ($2*0.5), \ '' using ($2*0.7)