Update: This has now happened two days in a row.

Update: XML of scheduled tasks and images now included.

Two servers located in London, both Windows 2012, have a scheduled task set to run at 3pm Monday to Friday. This has been set up for the last 5 months without a problem.

However, on Monday the 28th of August they both ran the scheduled task at 3pm and then again at 4pm. When it was first reported, I thought it was too much of a coincidence to be the day after the clocks had gone back an hour. However, I’m failing in being able to explain why it has happened and if it is related to the clock change at all.

The relevant logs from one server (the logs for the other follow this pattern as well):

Event 129 15:00:20 Task Scheduler launch task "\3pm", instance "C:\Program Files (x86)\PHP\v5.4\php.exe" with process ID 2388.

Event 100 15:00:20 Task Scheduler started "{75a3590f-dec1-4dee-bd27-73d63a50a9d7}" instance of the "\3pm" task for user "x\y".

Event 200 15:00:20 Task Scheduler launched action "C:\Program Files (x86)\PHP\v5.4\php.exe" in instance "{75a3590f-dec1-4dee-bd27-73d63a50a9d7}" of task "\3pm".

Event 201 15:00:23 Task Scheduler successfully completed task "\3pm" , instance "{75a3590f-dec1-4dee-bd27-73d63a50a9d7}" , action "C:\Program Files (x86)\PHP\v5.4\php.exe" with return code 0.

Event 129 16:00:20 Task Scheduler launch task "\3pm", instance "C:\Program Files (x86)\PHP\v5.4\php.exe" with process ID 1224.

Event 100 16:00:20 Task Scheduler started "{3dd46ca9-c525-4796-86b5-5e513fd45f26}" instance of the "\3pm" task for user "x\y".

Event 200 16:00:20 Task Scheduler launched action "C:\Program Files (x86)\PHP\v5.4\php.exe" in instance "{3dd46ca9-c525-4796-86b5-5e513fd45f26}" of task "\3pm".

Event 201 16:00:23 Task Scheduler successfully completed task "\3pm" , instance "{3dd46ca9-c525-4796-86b5-5e513fd45f26}" , action "C:\Program Files (x86)\PHP\v5.4\php.exe" with return code 0.

I've seen this question Scheduled task running twice from time to time which points to a bug at http://support.microsoft.com/kb/2461249 being the cause. However, this doesn't include Server 2012 in it's list of problem operating systems.

I’m struggling to explain this, can anyone else?

The XML export for the scheduled task is:

<?xml version="1.0" encoding="UTF-16"?>
<Task version="1.2" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <Date>2013-04-16T14:04:17.4897806</Date>
    <Author>x\y</Author>
  </RegistrationInfo>
  <Triggers>
    <CalendarTrigger>
      <StartBoundary>2013-04-17T15:00:20</StartBoundary>
      <Enabled>true</Enabled>
      <ScheduleByWeek>
        <DaysOfWeek>
          <Monday />
          <Tuesday />
          <Wednesday />
          <Thursday />
          <Friday />
        </DaysOfWeek>
        <WeeksInterval>1</WeeksInterval>
      </ScheduleByWeek>
    </CalendarTrigger>
  </Triggers>
  <Principals>
    <Principal id="Author">
      <UserId>x\y</UserId>
      <LogonType>Password</LogonType>
      <RunLevel>LeastPrivilege</RunLevel>
    </Principal>
  </Principals>
  <Settings>
    <MultipleInstancesPolicy>IgnoreNew</MultipleInstancesPolicy>
    <DisallowStartIfOnBatteries>true</DisallowStartIfOnBatteries>
    <StopIfGoingOnBatteries>true</StopIfGoingOnBatteries>
    <AllowHardTerminate>true</AllowHardTerminate>
    <StartWhenAvailable>false</StartWhenAvailable>
    <RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAvailable>
    <IdleSettings>
      <StopOnIdleEnd>true</StopOnIdleEnd>
      <RestartOnIdle>false</RestartOnIdle>
    </IdleSettings>
    <AllowStartOnDemand>true</AllowStartOnDemand>
    <Enabled>true</Enabled>
    <Hidden>false</Hidden>
    <RunOnlyIfIdle>false</RunOnlyIfIdle>
    <WakeToRun>false</WakeToRun>
    <ExecutionTimeLimit>P3D</ExecutionTimeLimit>
    <Priority>7</Priority>
  </Settings>
  <Actions Context="Author">
    <Exec>
      <Command>"C:\Program Files (x86)\PHP\v5.4\php.exe"</Command>
      <Arguments>-f "c:\a.php"</Arguments>
    </Exec>
  </Actions>
</Task>

29 October 17:00 - Update - Both servers have again run the scheduled task at 15:00 and 16:00. I've now updated the php file that is run by the scheduler to not actually do anything whilst I'm going through trying to solve this. I'm planning on restarting one server to see if this changes anything tomorrow.

30 October 08:25 - Update - When exporting the task XML I remembered that I hadn't included the fact that the scheduled task on second server was created by importing the XML of the task created on the first. The only difference between the two tasks is the path of the php file they are executing and the user account that they are running as.