Computers have a simple way of keeping time: generally, they count seconds. Real Computers -- those running Unix-like operating systems -- count the number of elapsed seconds since midnight January 1 1970, UTC. As I write this, it's about 1299218806 in this system. That number, often called "Unix time" or a "time_t", is the same in Baltimore, London, or Tokyo. Simple.
But as experienced by us biological organisms, trying to keep our activities somewhat in sync with the diurnal light-dark cycle and the lengthening and shortening of the day over the seasons, time is much trickier.
Most of us only have to think about that when we change the clocks in the spring and fall, or when traveling to a new time zone. But on the internet, a computer in Baltimore might be connected to one in London, several timezones away; and those computers might be analyzing data containing timestamps -- not time_ts like 1299218806, but human-meaningful times like March 4 2011, 1:06:46 am -- from months ago, when daylight savings time was (or wasn't) in effect. Or even from years ago, when the very rules governing daylight savings time were different. Trying to convert from, say, October 31 1985, 7:00 pm Eastern Time to a pure number, or even to UTC time, requires being able to figure out if daylight savings time was in effect in the Eastern time zone at that moment -- a fairly complex question, as the rules have changed twice since that date!
Timezone information is used in such important Internet protocols as DHCP (the protocol that lets your laptop get an IP address -- as well as the local timezone -- from the WiFi service at the airport) and iCalendar (which is what lets you coordinate your meetings via Google Calendar -- or if you're stuck in hell, Outlook).
To keep it straight, since the early 1980s a group of volunteers has maintained the "TZ Database" -- a.k.a. the Olson Database, after its founder, Arthur David Olson. It's an amazing document, as Jon Udell reports -- rich with bits of history and politics.
Now Olson is preparing to retire, and IANA (the Internet Assigned Numbers Authority) is considering how to hand off maintenance of the vital bit of infrastructure to someone new.
It's a good opportunity to stop and reflect on how much of this Internet that we take for granted relies on volunteer efforts -- cyber-Tzadikim Nistarim, if you will.