Timezone Database Online?

[rwk at americom.com]

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.