[Solved]-NVD3: multiChart wrong format for series-d3.js

You could do the following:

1. Define a function that converts epoch to a nice date. Something like this:

   function epochToNiceDate(epoch) {
       var date = new Date(0);
       date.setUTCSeconds(epoch);
       var day = date.getDate();
       var month = date.getMonth() + 1;
       var year = date.getFullYear();
       return day + "-" + month + "-" + year;
   }
   

2. Pass a content generator function for your tooltip to your chart (assuming you have useInteractiveGuideline enabled). You could browse the source code of NVD3 and copy/paste the default content generator and then modify it as you wish. Let's use the following one as an example:

   chart.interactiveLayer.tooltip.contentGenerator(function (d) {
       var tooltipTitle = epochToNiceDate(d.value);
       var tooltip = "";
   
       tooltip += "<table>";
       tooltip += "<thead>";
       tooltip += "<tr><td colspan='3'><strong class='x-value'>" + tooltipTitle + "</strong></td></tr>";
       tooltip += "</thead>";
       tooltip += "<tbody>"
   
       for(var i in d.series) {
           var currentSeries = d.series[i];
           var color = currentSeries.color;
           var key = currentSeries.key;
           var value = currentSeries.value;
   
           tooltip += "<tr>";
           tooltip += "   <td class='legend-color-guide'>";
           tooltip += "      <div style='background-color: " + color + ";'></div>";
           tooltip += "   </td>";
           tooltip += "   <td class='key'>" + key + "</td>";
           tooltip += "   <td class='value'>" + value + "</td>";
           tooltip += "</tr>";
       }
   
       tooltip += "</tbody>";
       tooltip += "</table>";
   
       return tooltip;
   });
   

You can see it in action here: https://jsfiddle.net/Luc93/qf4u5439/

Good luck!