[TYPO3-calendar] Own marker with userfunc

[Sven Krause]

Hello,

I  generate a new marker for the list view and like to parse the value with
an userfunc to get  a timestamp.
 
plugin.tx_cal_controller.view.list.event {
    starttag = COA
    starttag {
        1=TEXT
        1 {
           field=start_date
           postUserFunc = user_mktime->main
          postUserFunc.field = start_date
      }
    }
}

By debugging with echo t3lib_div::debug($conf,'Userfunc'); it returns
start_date and not the value from the database. Whats wrong?

Greetings, Sven