Community Builder Date

Ok, I check it now once more, but -1 day is whenever I enter the date

Servertime = GMT +1 (Vienna)
Joomla Controlpaneltime = Vienna
CB Field Date Offset = OFF

If enter a day e.g. 26th I get 25 after saving the user
Also check this with fieldtype 'birthday' = same bad result

There is no effect if switch Date Offset = ON, and also no other effect if delete the field, and create it new with other seletions. Test the same with UTC Time, also set ALL to UTC

Then you're probably out of date. Please update and retest. There were some offset problems which are now fixed. It was doing offset from GMT instead of using timezones. When doing offset it can't figure out that in 2011 for example it might have been DST, but with timezones it can. We now use timezones for the JS usage like we do for the PHP usage. Latest release does not offset Date fields at all (in JS or PHP) so your issue is literally an impossibility unless something else is modifying the data.

I use 2.0.15+build.2016.12.08.00.30.40.f93e49b89 and PHP 7.0.11 for latest test I wrote.

Then I'm out of ideas as to what is causing your issue. I'm not able to confirm your issue regardless of timezone settings as again the Date field entirely ignores them now. Even using your exact settings I am unable to confirm. You couldn't have been using latest release if you're still seeing that offset parameter for a Date field. Are you sure you're not using a Datetime field? They are two different fieldtypes.

Edit: Noticed you're on PHP 7. Maybe that's the cause? Are you able to downgrade to PHP 5.6 and see if issue persists?

may be because use not english as language?

Language shouldn't have anything to do with the timezone offset of fields. That parameter is flat out removed for Date fields in latest CB build. It doesn't exist anymore. If you're still seeing it you're either out of date or you are using a Datetime field.