Date Difference and different dates

Thursday 31 July 2008This is 15 years old. Be careful.

Date Difference
My son Max released his first app last week: Date Difference is a small OS X application that simply gives you the time delta between two dates. It’s been fun helping him puzzle through Objective-C, Cocoa, dates, and all the rest of the details that go into even a very small application. Go give it a try. With it, we realized that Max is coming up on his 6000-day birthday.

It’s also been an interesting jumping off point for talking about all of the weirdnesses with time and dates. First off: time zones. Although motivated by physical reality, time zones are really political creations, and so can be very random. Some are not even whole numbers of hours. In fact, Iran, Afghanistan and Myanmar are all in the small club of countries a half-hour out of step. Perhaps an explanation for bad behavior? Think about it...

Another date anomaly: switching from the old-style Julian calendar to the more accurate Gregorian calendar meant correcting accumulated error by skipping days. For example, in Britain and its colonies, the day after Sept 2, 1752 was Sept 14, and in Russia, Jan 31, 1918 was followed by Feb 14. Hard to imagine the logistics of making that happen.


Cool!! Always nice to see the next generation getting involved.

Another bizarro topic is daylight savings time. Some countries have (or had) fairly normal models for it. Occasionally we get someone like Bush that tweaks it in the US. But some countries its a parliamentary decision that they make on a year to year basis. I once got into a debate with a marketing guy that wanted a sw algorithm for daylight savings time that worked in all regions of the world, ugh...
Steady with your new "axis of evil" - the whole of India and parts of Australia are half an hour out of kilter.
I knew someone would point out India and Australia! I guess I'm not cut out for international diplomacy after all! :)
Jocelyn Legault 4:23 PM on 1 Aug 2008
FYI, Nepal has even a 15 minutes time zone!!
Try running "cal 9 1752" on a Unix machine.

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