start_epoch = 0 on chrome test

[rikiki61]

Hello,
I verified that in tests performed with chrome
..../results.php?test=XXX&f=xml

Code:

<response>
  <data>
    <average>
      <firstView>
        <start_epoch>0</start_epoch>

....

how can I find out the exact time to start the test?

what is the recommended field for the given time of the test to be inserted on the horizontal axis of a graph?

Code:

<response>
  <data>
    <completed>Fri, 18 May 2018 13:02:05 +0000</completed>

??

thanks in advance for the help