DateTime set to an hour earlier

I have an object of type Time startWorkingTime and object of type DateTime nextBusinessDay. I want to create new object of type DateTime based on startWorkingTime and nextBusinessDay.
Here is my code:

DateTime startWorkingTime = DateTime.newInstance(nextBusinessDay.year(), nextBusinessDay.month(), nextBusinessDay.day(), currentStartHours.hour(), currentStartHours.minute(), currentStartHours.second());

After startworkingtime the time is set one hour earlier
For example:

23:59:24:025 USER_DEBUG [188]|DEBUG|currentStartHours 09:00:00.000Z
23:59:24:025 USER_DEBUG [189]|DEBUG|currentStartHours.hour() 9
23:59:24:025 USER_DEBUG [197]|DEBUG|startWorkingTime 2017-08-04 08:00:00

Could you please explain why the hour in startWorkingTime is 08:00:00 and advise how to fix it?