thanks for bringing this up - let’s solve your issue right away.
There are two aspects leading to the unexpected behaviour.
The first thing is your format string. The capital letter M refers to the month, see here. So what you meant to write was most likely this format string: DD.MM.YYY - HH:mm. That will improve the result and remove the “mysterious 6”, but still display the date in UTC:
The reason is that Tape calculation fields always run in UTC, as they need to work the same for every user and organization. However, if you need to format the date relative in a certain timezone, it can be easily done using this code: