Actual action start and end time

There is some info here.
Summary is that this is not available in Session Relevance but possible via the REST API.

Example:

https://localhost:52311/api/action/399/status
<?xml version="1.0" encoding="UTF-8"?>
<BESAPI xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="BESAPI.xsd">
    <ActionResults Resource="https://localhost:52311/api/action/399/status">
        <ActionID>399</ActionID>
        <Status>Expired</Status>
        <DateIssued>Mon, 04 May 2015 01:09:51 +0000</DateIssued>
        <Computer ID="11577043" Name="TINTIN">
            <Status>The action executed successfully.</Status>
            <State IsError="0">3</State>
            <ExitCode>0</ExitCode>
            <ApplyCount>1</ApplyCount>
            <RetryCount>1</RetryCount>
            <LineNumber>42</LineNumber>
            <StartTime>Mon, 04 May 2015 01:11:16 +0000</StartTime>
            <EndTime>Mon, 04 May 2015 01:11:57 +0000</EndTime>
        </Computer>
    </ActionResults>
</BESAPI>