testdata = {
    {DateObject[{2017, 1, 1}, "Day"], 1, 486, 1, 2},
    {DateObject[{2017, 1, 2}, "Day"], 1, 487, 2, 3},
    {DateObject[{2017, 1, 3}, "Day"], 1, 487, 3, 4},
    {DateObject[{2017, 1, 4}, "Day"], 1, 486, 4, 5},
    {DateObject[{2017, 1, 5}, "Day"], 1, 487, 5, 6},
    {DateObject[{2017, 1, 6}, "Day"], 1, 485, 6, 7},
    {DateObject[{2017, 1, 1}, "Day"], 2, 476, 6, 7},
    {DateObject[{2017, 1, 2}, "Day"], 2, 487, 5, 6},
    {DateObject[{2017, 1, 3}, "Day"], 2, 497, 4, 5},
    {DateObject[{2017, 1, 4}, "Day"], 2, 410, 3, 4},
    {DateObject[{2017, 1, 5}, "Day"], 2, 411, 2, 3},
    {DateObject[{2017, 1, 6}, "Day"], 2, 412, 1, 2}}

head = {"nr1" -> 2, "nr2" -> 3};

FormPage[{ "kop" -> {head} -> 2},
 (testdata1 = TimeSeries[Map[Flatten, testdata, {-4}][[All, {1, #kop}]]];
   DateListPlot[testdata1,
    , PlotStyle -> {Red, Thick}
    , PlotTheme -> {"Scientific", "Wide", "Sans"}
    , PlotLegends -> "Expressions"
    ]) &
 ]

FormPage[{ "kop" -> {head} -> 1},
 DateListPlot[
   Select[Map[Flatten, testdata, {-4}], #[[2]] == #kop][[All, {1,
      3}]]] &
 ]