Daylight Savings Time

This weekend we will be experiencing a semi-annual event that causes havoc with our clocks and watches: daylight savings time. In the spring we change from standard time to daylight time. In the fall, we go back to standard time. The idea behind the time change is that going on daylight savings time means we will use less electricity in the evenings for our lights. It was a good idea until air conditioning became so common. Now it is a toss-up as to if it saves any energy at all. One thing that is certain is that we all spend a lot of time adjusting clocks around our offices, homes, and wrists.

Computers also have to deal with daylight savings time. Most home computers are smart enough to automatically adjust themselves. So what happens with sophisticated servers? In the spring, we jump forward an hour and so it instantly goes from 2am to 3am. In the fall, we jump backwards from 2am to 1am. If there are any scheduled jobs meant to run between 1am and 2am, they get executed again. The autumn can be a good thing if every night at 1:30, the bank deposits extra money in your account. You get 2 deposits instead of 1. However the bank rarely just gives away money. The more common case is that they will charge a fee. In the fall, you will get charged twice and that can be a bad thing.

The way most servers get around daylight savings time is by staying on one timezone and that is generally UTC or universal coordinated time. Doing so keeps the time the same even during the spring and fall semi-annual time changes. This can save a lot of hassle. Trust me on this one as I had to move one of my servers from PDT to UTC this evening. The time change caused a lot of problems in the spring and was poised to do even more this next Sunday morning. Now I can sleep more soundly on Sunday evening and don't have to worry about fixing stuff on Monday morning.