Шаг подписи оси X - время

set term png
set output '/migration/current/tmp/reporting/w+Vd7SehGqyZpKdEDFTUEQ.png'
set xdata time
set timefmt "%Y-%m-%d/%H:%M:%S"
set format x "%Y-%m-%d\n%H:%M:%S"
set xrange["2015-03-30/14:34:45":"2015-03-31/14:19:49"]
set terminal png size 640,480
set xtics font "DejaVuSans,5"
plot "/migration/current/tmp/reporting/fvSifIFxIYRECNLa64AD2A/1.dat" using 1:2 with lines notitle

2015-03-30/14:34:45 26.4
2015-03-30/14:34:45 26.4
2015-03-30/14:49:45 27.0
2015-03-30/15:00:45 26.9
2015-03-30/15:04:45 26.7
2015-03-30/15:19:45 27.4
2015-03-30/15:25:25 27.5
2015-03-30/15:25:28 27.5
2015-03-30/15:30:30 27.5
2015-03-30/15:34:45 27.2
2015-03-30/15:49:45 27.1
2015-03-30/16:00:40 27.4
2015-03-30/16:00:40 27.4
2015-03-30/16:00:45 27.4
2015-03-30/16:04:45 27.4
2015-03-30/16:19:45 26.8
2015-03-30/16:33:00 26.7
2015-03-30/16:34:45 26.7
2015-03-30/16:49:45 26.5
2015-03-30/17:00:45 26.4
2015-03-30/17:04:46 26.3
2015-03-30/17:05:41 26.3
2015-03-30/17:08:01 26.3
2015-03-30/17:19:46 26.2
2015-03-30/17:21:36 26.2