From LimeSurvey Manual
Language & time
- defaultlang: This should be set to the default language to be used in your administration scripts, and also the default setting for language in the public survey list. This setting can be overridden in the global settings dialog or edited in config.php.
- timeadjust: If your web server is in a different time zone to the location where your surveys will be based, put the difference between your server and your home time zone here. For example, I live in Australia, but I use a US web server. The web server is 14 hours behind my local time zone. So my setting here is "14". In other words, it adds 14 hours to the web servers time. This setting is particularly important when surveys timestamp the responses. This setting can be overridden in the global settings dialog or edited in config.php.