At Time Zone

Rob Farley looks at the AT TIME ZONE operation in SQL Server 2016:

But despite the longwindedness of it, I love it, because at no point did I need to figure out that Adelaide was in +10:30, or that Eastern was -5:00 – I simply needed to know the time zone by name. Figuring out whether daylight saving should apply or not was handled for me.

It works by using the Windows registry, which has all that information in it, but sadly, it’s not perfect when looking back in time. Australia changed the dates in 2008, and the US changed its dates in 2005 – both countries saving daylight for more of the year. AT TIME ZONE understands this. But it doesn’t seem to appreciate that in Australia in the year 2000, thanks to the Sydney Olympics, Australia started daylight saving about two months earlier. This is a little frustrating, but it’s not SQL’s fault – we need to blame Windows for that. I guess the Windows registry doesn’t remember the hotfix that went around that year. (Note to self: I might need to ask someone in the Windows team to fix that…)

Like most companies dealing with multiple time zones, we ended up building a table and function to translate.  This is a nice, built-in way of doing something very similar.

Related Posts

Using DATEADD Instead Of DATEDIFF

Michael J. Swart points out a bit of trickery with DATEDIFF: I assumed that the DATEDIFF function I wrote worked this way: Subtract the two dates to get a timespan value and then return the number of seconds (rounded somehow) in that timespan. But that’s not how it works. The docs for DATEDIFF say: “Returns the count (signed integer) of […]

Read More

When AT TIME ZONE Is Too Slow

Robert Davis troubleshoots a performance problem relating to time zones: Time Zones were definitely being a drag today. I got an email from one of the developers at work asking about the performance difference between 2 queries. The only difference between the 2 queries is that one of them uses the AT TIME ZONE clause that was […]

Read More

Categories

July 2016
MTWTFSS
« Jun Aug »
 123
45678910
11121314151617
18192021222324
25262728293031