From HostThyself

Timezone is an interesting issue in global Internet. Consider a scenario like this

The datacenter is in country A with timezone X, you are in country B with timezone Y and your client is in country C with timezone C.

Typically, the default timezone is set by the person who install the server, usually this would be the datacenter. When you upload files or read time form the system or look at server logs, the time can be confusing.

A solution is to set the server time to UTC (Universal Co-ordinated Time) and let each user figure out their offset from UTC.