My server is set up correctly - there are lot of other sites (Joomla, Wordpress) and everywhere time is correct.
I have also Moodle 2.5 (Attendance module build 2013082901) platform on the same server, and times do not change in summer/winter time.
I have added issue in here: https://github.com/danmarsden/moodle-mod_attendance/issues/176