Joi Ito's Web

Joi Ito's conversation with the living web.


I'm so sick of time zones and daylight savings and my blog posts being all funky because of it. I've tried it before, but haven't been able to do it well. I'm going to try it again. I'm setting the clock on my computer to UTC and would like people to tell use UTC with me when appropriate. For instance, when scheduling telephone calls.

It actually makes it much easier if you convert to UTC for me. There are too many moving parts otherwise. In the southern hemisphere, the daylight savings goes the opposite direction of daylight savings in the north. In addition, different countries switch on different days. Then there are countries like Japan that don't observe daylight savings. So when people try to tell me to do something in some country, it sometimes requires two lookups - any adjustments in my country and any adjustments in the original country. Using UTC reduces the chance of error by forcing people to only track the +/- UTC in their own time zone. At least that's the theory.

Time and and The World Time Server are good sites for checking what time it is anywhere and Aion is a good OS X menubar thingie to show you all of the times in various time zones. Haven't tested for the preciseness of the daylight savings switches, but seemed OK the last time around.

UPDATE: Does anyone know of a good authoritative list of time zones and daylight savings switchover dates?


I started using UTC more when I started living in Europe part of the year. One doo-dad that helps on my blog, some javascript for formatting relative timestamps. A blog post identified as "4 hours ago" is a lot better than "5AM" in some unknown timezone.

As the world Internet community (singular) continues to take precedence over the older conventional geographical communities (plural) we no longer "live" at our current physical local address. I am very heartened that you would consider this most complex paradigm shift.

As an early adopter of the Swatch Beat I recognized three things. First it was way ahead of its time (excuse the pun). Two, it was seen by many as a clever marketing ploy to try and corner the time market. This was shunned by many for just that reason. Over shadowing the previous two concerns, Beat tried to provide the time-link that the Internet community really needs - a unified time-link that UTC can and will provide.

Sadly we have an nearly insurmountable obstacle to overcome - the length of human history that judged time by the amount of light in their given environment. I am sure that someone much smarter than me would talk about the sociology of time while someone else might touch on the collective conscience of time.

I applaud your initiative. In some small part I too have undertaken a similar attempt. Where I have encountered the most difficulty is in the computer systems themselves. They insist on 'handling' time in the 'Time Zone' paradigm automatically. This, like so many other 'services', are automated so that we puny humans do not have to concern ourselves with it. Regrettably we are then...

"Locked in our box,"

- Papa

+++++++++++++! Amen brother! At least you didn't try and go with Swatch time :-)

We've been using UTC for internal scheduling of global meetings at Metroblogging for a while, it took a little to get people used to the idea but once they figure it out it makes so much more sense then trying to calculate for the qwerks of each little area of world and how they happen to look at time. I'm all for it. Now if I could just get a UTC app for my phone I'd be set.

like william, i saw the purity of swatch's beat when it was announced and tried hard to adopt it. my biggest barrier at the time was 99% of my contact was with people in my own country. now that even the countrymen i know are so often in a different place, it is starting to make much more sense.

i liked swatch's beat, not just because it was universal, but also because the fact that nothing on on the conventional clock is base 10 constantly annoyed me. and confused me. but in the end i realized it was a commercially proprietary system, which sorta bugged me (although i think swatch offered to license it for free).

i think the good thing about the beat is that not only does it divorce time from time zones, but also from the traditional way of calling out time. although you and i don't have meetings, if you say "let's talk about this at 0800 zulu" i'm going to think "8 am, yah i can do that" just because 0800 sounds like a time i know. even though 0800 zulu is 0300 here. (or 0400). most brains, because they aren't used to dealing with utc, don't make the shift. with the .beat it forces a shift in thinking out of local time zones.

and sean, if you still use a palm treo, there's even a .beat application for it that converts time for you.

wow do i sound like an ad for swatch or what? sorry. i don't mean to try and push their commercial venture. i just think it presents less usability issues than zulu time. and i'm sorry i can't call it UTC or universal. isn't zulu so much more fun to say. the american military got two monikers right: zulu and klik.

p.s. i just reloaded this page only to see the UTC clock as an image up top. do i need to point any further than that image (or script or whatever you want to call it) to point out the awful usability of UTC? now every hour tick represents two hours? that's absurd. who can tell time on such devices? i realize that if joi chose a digital clock i probably wouldn't have such complaints, but he did. and i assume you did for a reason.

Joi, we just made the same decision at Global Voices, about a week ago - it would be interesting to see other international projects and internationalists making the same decision...

Living in Australia, communicating with people around the globe, the whole time thing is a real challenge. I find the most useful tool is the Meeting Planner function in If I want to schedule a conference call with people in, say, Sydney, Dallas, London and Shanghai, I can line up all those cities and see at a glance which time is going to be the best compromise for all.

perfect timing - I love that I can quote you on one of my slides tomorow as timezones and the american way of referring to theirs drives me nuts as well; having them to at least think in UTC helps me tremendously as Germany usually is GMT+1 - if they 'speak' in GMT that's easy to do.

swatch @time was elite

now I'm using 'ST' which is CST (WoW Server Time =D)

time is a construct we work with

I have the distinct honor of having switched GVO and Joi to UTC.
(it is done sir ;)

Thanks Boris.

We use UTC exclusively on english wikipedia, it would be a nightmare otherwise. I'd be happy to switch to it for normal day to day planning, but it will probably have to be out of necessity for most to switch.

Faced with the same problem that many of us have, I ended up building my own site. Sure it does what many other sites do- tells the time in each country and city, but I have added a time difference feature. You can plug in where you are calling (or going to) followed by where you are (or were) and it will give you a printable chart for the times against one another.

If anyone is interested, you can find this feature at (it gives an expiry date as well for when one of the locations changes their clocks).

Drop me a mail from the site if you have any comments or suggestions for improvement.

Joi, you are slipping! Where is the how-to on setting OS X to UTC? Here:


/me deletes from Joi's Applications folder.

UTC is the standard among amateur radio people for a very long time (at least for 50 or more years). My wrist watch has been set on UTC since 1975 (during my life in the USA, where I first thought about what the time zones are). So your choice of UTC sounds quite logical to me.

On the other hand, UTC introduces the leap seconds, which may cause troubles among machines (which require continuous monotonic time increasing). So I use TAI (atomic-clock based time which does not have the leap seconds) for my servers.

I think UTC is sufficient for human beings.