Timezone Database Online?

I ran across your this address as a source of up to date timezone information, world wide. Can you refer me to a URL with more information... Or one for a complete up-to-date and authoritative database of timezones, their names, offsets from GMT, and when/if they use summer hours (daylight savings time)? Can you tell me also... Are the dates "summer hours" go into effect standardized worldwide? And if not, is there any source for this information? We would like to be able to compute the current time (in any timezone) taking the possibility of "summer hours" into account. Thanks for any help, Dick Kreutzer AmeriCom Inc.