What is this?

It's a pretty clock that shows you accurate time around the world, and shows you whether your computer's clock is set correctly. Made by me.

Where'd the inspiration come from?

“Erhard Ratdolt, Peter Loeslein, and Bernhard Maier, pages from Calendarium, by Regiomontanus, 1476. The two top circles are printed on heavy paper, cut out, and mounted over the larger woodcut with tape and a string. This may be the first ‘die-cut’ and manual tip-in graphic material in a printed book.”

Meggs, Philip, and Alston Purvis. Meggs’ History of Graphic Design. 4th edition. New Jersey: John Wiley and Sons, 2006. p. 96.

What are the accuracy readings all about?

The calendarium shows the time according to my webserver’s clock (which I’m assuming is pretty close to the world standard).

It does this by asking the server for a “sample” of the time. Of course, it takes time for information to travel through the tubes, which compromises the accuracy of the sample. So the first reading indicates how far off the calendarium might be from the server clock. (Specifically, it’s give-or-take half the time it took to get the sample.)

The other reading shows how far off your computer’s clock is from the server clock. This also takes into account the latency issue described above.

But isn’t that kind of stupid since modern computers automatically synchronize their clocks?

Yeah, a little. But maybe you forgot to turn your synchronizer on? Or perhaps you want to check and make sure it’s working.

What happens if it takes too long to get the time sample from the server?

If it takes more than five seconds, the sample is as good as dirt. So the calendarium will just show the time according to your computer’s clock.

The time is correct, but the time zone is one hour ahead of mine. What gives?

Are you observing Daylight Savings Time where you are? The calendarium tries to guess your zone by how your computer’s clock is set, but it’s not smart enough to tell whether you’re observing DST. You can fix it by selecting the correct time zone, and then checking the box for daylight saving time to add an hour. The address will change so you can bookmark it like that if you want.

Geek Note: If I had written the time zone functionality in Flash rather than JavaScript, I might have been able to solve this problem ... I think Flash knows more about the user’s time zone rules (e.g. whether DST is observed and whether it is in effect) than JavaScript does. All I can do with JavaScript is compare the user’s local time with UTC. Oh well.

Today’s the 12th, but the calendar wheel says it’s the 13th. What gives?

Is it close to midnight where you are? All the dials on the calendarium move continuously—they don’t jump from one value to the next like a digital clock. You know the hour doesn’t really change until the minute hand gets to 60; in the same way, the date doesn’t really change until the hour hand gets to midnight.

What’s with the zodiac dial?

It tells you which constellation is behind the Sun during the day, in case you ever need to know.