I am trying to troubleshoot a problem. Some very helpful information would lead me to a solution is: Often does Linux check the /etc/localtime file? Additionally if there is a configuration file to increase the frequency (for testing) that would be helpful. Normally I would assume that it would check when a call to the ntp server has been executed, but NTP is not installed. It couldn't possibly check every time the date function is called as this would result in many problems on busy web servers. Server is Ubuntu 12.04, but I don't think that is relevant to the question.