In my last post I reminisced about an airline sending its passengers out early due to poorly coordinated clocks. But even when the clocks are right, there is something else that can let confusion reign: The Time Zone and its good friend Daylight Savings Time (DST).
In the late 90s when I worked at Mainframe accounts, we would always get an hour at the end of daylight savings to get in some urgent maintenance. Why an hour? Because when we set the clocks back at the end of DST the client would have to shut everything down for that hour.
The reason being that transactions were being logged in local time. So if the local time went backwards by one hour then transactions logged in the subsequent hour would appear to be earlier than transactions logged in the previous hour! This could not be allowed to happen so the simple solution was to allow no transactions to occur at all.
The solution to this madness was to switch to logging all transactions in GMT (or UDT) and then log a local offset to reflect what the local time was as the time of the transaction. I worked with one New Zealand Bank who had set up their systems to believe that local time actually was GMT (instead of +12 from GMT). They had to shut their systems down for a total of 12 hours (across multiple weekends) to correct this sin. Painful.
It’s bad enough living in Australia where in Summer we have five time zones (Western, Central, Central DST, Eastern, Eastern DST).
Compare this to China (1.3 billion people in a nation 4893km east to west) or India (1.2 billion in a nation 2933km East to West) where both nations use single time zones. Australia in comparison is a nation of 22 million with up to 5 time zones (though admittedly it is also quite wide (east to west), at 4100km). I wonder if anyone has ever written a PhD paper on the economic benefit of a single timezone?
Not that I am planning to urge Australians to abandon their resistance to universal daylight savings, but when you have worked in IT support this is yet another variable you need to struggle with. Especially as our governments keep monkeying with the start and stop dates (something that has caused all manner of unforeseen issues). My single advice is to not only use NTP, but to ensure the timezone is set correctly on all of your IT infrastructure. I have talked about the Brocade Logon panel of shame in the past, but the timezone of shame is close behind. This switch is not in England and yet it’s timezone is UTC.
For many products, timezone changes only take effect after a reboot, so it’s vital to get them set at install time. You don’t want to have an issue, then during investigation have that issue compounded by confusion about date stamps due to mixed time zones.
And if you are looking for help with time zones and you are a Mac or iPhone user, I can strongly recommend Time Scroller, an app I use on a very regular basis.
Recommendations for other apps are very welcome.