[TYPO3-calendar] Set list.starttime to page:starttime

[Meggie]

I added a calendar list to the newsletter so only the events of the next 30 days depending on the date of the (newsletter-)page shall be shown. So I need to define the list.starttime not as a relative date but as a fixed one.
endtime= +30 days works fine, but definig starttime doesn't work! Not even by writing the date directly! I tried several date formats as "20170704", "2017-07-04", "04.07.2017", "04 July 2017" etc.!

lib.terminListeNewsletter = COA
lib.terminListeNewsletter {
  1 = LOAD_REGISTER
  1.startdatumNewsletter = TEXT
  1.startdatumNewsletter.data = page:starttime // page:crdate
  1.startdatumNewsletter.strftime = %Y%m%d
    
  10 < plugin.tx_cal_controller
  10 {
  pidList = 53
    view {
      allowedViews = list
      list {
        listTemplate = fileadmin/OeLB/Extensions/cal/list.tmpl
        maxEvents = 100 
        pageBrowser.usePageBrowser = 0

      # starttime.data = register:startdatumNewsletter
        starttime= 04 July 2017

        endtime= +30 days        
      }
    }
  }
}