'Daylight Savings Bugs' Loom

An anonymous reader writes "ZDNet has front page coverage of the looming daylight savings changeover, and the bugs that may crop up this year. With the extension of daylight savings time by four weeks, some engineers and programmers are warning that unprepared companies will experience serious problems in March. While companies like Microsoft have already patched their software, Gartner is warning that bugs in the travel and banking sectors could have unforeseen consequences in the coming months. ' In addition, trading applications might execute purchases and sales at the wrong time, and cell phone-billing software could charge peak rates at off-peak hours. On top of that, the effect is expected to be felt around the world: Canada and Bermuda are conforming to the U.S.-mandated change, and time zone shifts have happened in other locales as well.'" Is this just more Y2K doomsaying, or do you think there's a serious problem here?

Comments

Re:Things you should know.

[Ubergrendle]

Our datacentre has ~ 500 Solaris / HP-UX / AIX boxen, and ~ 1000 Windows servers.

15 minute change window to apply patch, another 15 minutes to reboot successfully and come back online. Multiply 30 min x 1500 = 45,000 minutes, or 750 hours. But we only have one weekly change window, Sunday mornings from 2-6am. Assuming finite number of staff, contingency (there's always going to be some problems), etc... we started last September. We might just make the deadline.

So yes, I think its a bit of a problem. There's also the unspoken assumption that people learned their lessons during Y2k and have sufficient date handling logic to address changes to DST...nothing hard coded in the underlying applications.

Already has ramifications

[michaelmalak]

Newer JDK's already have the new time zone rules encoded, and this can cause subtle bugs to suddenly surface. It turns out that Date.equals() does a deep object compare, including the time zone rules (not just which time zone you're in, but the rules regarding when daylight savings starts and ends). Thus if you have multiple JVMs involved, such as one on a database server and one on an application server running slightly different JVM revs (e.g. 1.4.2_08 vs. 1.4.2_11), then naive date comparisons (using equals() instead of equality on getTime()) can fail.

Re:Y2K was an oddity and mis-explained

[LMacG]

"In no way were dates routinely stored as two byte characters (99 being the max) when 1 byte would get you to 255 easily." Wrong. In EVERY WAY dates were routinely stored as three sets of two byte characters.

What you are completely ignoring is that the vast majority of the code that had to be examined and patched was written in COBOL. COBOL that store dates as a string of six digits. Digits that were stored in many cases as EBCDIC characters, not hexadecimal integer values. And just to make it fun, in some cases the source code was not available.

"[A]nyone that created a four digit date by String Concat: "19" + String(date) would " probably not have been born yet when the programs that needed to be fixed were written. It wasn't the programs that were written in the 1990's that had to be dealt with, it was the ones written in the 1960's. And if you don't believe there were any of those in use, then I suggest you have no idea what's really happening at your bank. Or in the US air traffic control system, for that matter.