Exactly one hour. Hmm, could it be a Daylight Savings / Summer Time issue?

Maybe. I think that problem became relevant after windows update time zone. FireFox 33.1 installed On my friend's computer and on my computer too. But his time zone is UTC+10:00. His didn't installed windows time zone update and his result of command "new Date(2014, 0, 1) " is "Date {Wed Jan 01 2014 00:00:00 GMT+1000}"