Sri Lankans are not known to keeping to the right time, but at least you can try to keep your computers so.
On Windows XP if you double click on the clock in the task bar you will get a dialog that has a “Internet Time” tab. Both time servers in this screen was not working for me.
I changed it to time-a.nist.gov from this list of the Simple Network Time Protocol (SNTP) time servers that are available on the Internet. It seems my work computer was a few minutes off.
On Ubuntu you can find these settings under the menus System -> Administration -> Time and Date. You can change the Configuration to Keep synchronized with internet servers, and add servers from the Time servers.
Update: Looks like Redmond has noticed Sri Lanka’s current time zone.