[ksevelyar]

Вопрос решён:

...
  var flot_options = {
    series: {
      lines: { show: true },
      points: { show: true },
    },
    colors: ["#000", "#dba255", "#919733"],
    xaxis:{
      mode: "time",
      timeformat: "%d",
      ticks: 31,
      minTickSize: [1, "day"],
      min: (new Date(prev_date)).getTime() + 14400000,
      max: (new Date(cur_date)).getTime() + 14400000,
    },
    grid: {
      borderWidth: 0
    }
  };

  var chart1_flot_options = { colors: ["#2fbd8d"] };

  var chart1_flot_options = $.extend({}, flot_options, chart1_flot_options);

- unless @data_1.empty?
  :javascript
    $.plot($("#chart_1"), [#{@data_1}], chart1_flot_options);