Jeff Duntemann's ContraPositive Diary

There is much scratching-of-heads today in the US and Canada about the Daylight Savings Time "crisis." Congress fiddled the dates this year to save energy (a good thing) but Windows by default assumes the 1996 start/end dates for DST in those parts of the country that use it. Microsoft posted a diabolically scary support page for changing the DST dates, but that's unnecessary now. A chap has written a simple but completely sufficient utility to update the DST dates not only on the host machine, but also any machine on your network—assuming you have a domain applied to your network. (As best I can tell, you can't run it remotely if you're still using a workgroup to hold your network together.)

The utility is Johnny5's DaySaver 1.5, and it's free and open source. (I found it through SourceForge.) It's a small, standalone .exe that needs no installation. I tested it on a virtual machine, and then ran it on all the other machines here. You run it, reboot, and you're there.

Here's what it does: Windows keeps the DST start/end dates in Registry keys, with one key per time zone. This allows states like Arizona to opt out of DST. DaySaver applies a change to all the Registry keys defining all affected time zones, and although the default list contains all the time zones in the US and Canada (where the 2007 changes apply) you can select any time zone on Earth if you want. For this change, keep all the defaults, for both time zones and start-end dates.

DaySaver is a network app. It works through IPs, even if you only want to change the machine you run it on. For the local machine, it uses the loopback IP (127.0.0.1) and for remote machines requires that you log in to each remote machine using hostname or IP, domain, and password. (This can be done using a list of remote machines stored as a text file.) Your firewall may pop up and ask permission to let it run, even on the local machine.

DaySaver hasn't been tested under Win9x or ME, and Pete Albrecht couldn't get it to run on his Win98 laptop. Consider it a Win2K/XP utility. Vista already has the fix built-in.

Note well: DaySaver makes Registry changes. It does not change the system time. (You have to reboot or run your NIST timesetter utility to do that.) Back up your Registry or set a restore point before running it. The good news is that once you run it, you don't need to run it again until such time as the Powers change the DST start/end dates. I also think you don't need to run it in Arizona, or in other places where DST doesn't apply and you have the DST box un-checked in the Time Zone tab of your Day/Time properties dialog.

Works great. Mostly targeted at Windows sysadmins (and thus not for beginners) but it's way better than making manual Registry changes. Highly recommended.