@steemchiller, you are right - it's always the time zone which is not considered in steemit. It was the same issue with the second conversion. Thank you for your fast help - it prevents me from having a 'sleepless night' about what could have gone wrong...

I tried to find the window you included in your answer on steemworld.org - but couldn't find it. Maybe it's well 'hidden' or on another site? Thanks again... @retinox