Comments on: Sorting TimeZoneInfo.GetSystemTimeZones() properly

By: Graham

Graham — Fri, 04 Sep 2009 07:34:58 +0000

Very useful post! There is a line missing from the VB code. Here is the full working code:

Public Function GetSensibleSortedTimeZones() As List(Of TimeZoneInfo)

Dim timeZones As List(Of TimeZoneInfo) = New List(Of TimeZoneInfo)(TimeZoneInfo.GetSystemTimeZones())
timeZones.Sort(New Comparison(Of TimeZoneInfo)(AddressOf CompareTimeZones))

Return timeZones

End Function

Private Function CompareTimeZones(ByVal left As TimeZoneInfo, ByVal right As TimeZoneInfo) As Integer

Dim comparison As Integer = left.BaseUtcOffset.CompareTo(right.BaseUtcOffset)
‘ If BaseUtcOffset identical then sort by DisplayName as well
Return IIf(comparison = 0, String.CompareOrdinal(left.DisplayName, right.DisplayName), comparison)

End Function

By: Barack Obama

Barack Obama — Fri, 12 Jun 2009 02:25:27 +0000

Another way to do this is to use Linq:

TimeZoneInfo.GetSystemTimeZones().OrderBy(Function(zone As TimeZoneInfo) zone.BaseUtcOffset.TotalHours)

By: Tatham Oddie

Tatham Oddie — Tue, 12 Feb 2008 03:56:28 +0000

Hi Whitney,

I have updated the post accordingly.

Thanks for your comment!

Tatham

By: Whitney Kew

Whitney Kew — Sat, 09 Feb 2008 22:43:21 +0000

Unfortunately, it looks like the angle brackets were removed in my last post; of course, List should be List (left angle bracket)TimeZoneInfo(right angle bracket).

By: Whitney Kew

Whitney Kew — Sat, 09 Feb 2008 22:40:51 +0000

Great find, thanks! However, the time zone order that I get is not exactly the same as that in the canned Windows time zone dialog box. By using just the base UTC offset for comparison, I get time zones with the same base UTC offset that aren’t always sorted alphabetically, like they are in the Windows dialog. For instance, the time zones I get back with a UTC offset of GMT-06:00 are, in this order:

(GMT-06:00) Central Time (US & Canada)
(GMT-06:00) Central America
(GMT-06:00) Saskatchewan
(GMT-06:00) Guadalajara, Mexico City, Monterrey

In the Windows time zone pull-down box, the order is alphabetical:

(GMT-06:00) Central America
(GMT-06:00) Central Time (US & Canada)
(GMT-06:00) Guadalajara, Mexico City, Monterrey
(GMT-06:00) Saskatchewan

So, I added a secondary comparison based on TimeZoneInfo.DisplayName, using String.CompareOrdinal() (from using Reflector to see how .NET does its display name comparison):

List timeZones = new List(TimeZoneInfo.GetSystemTimeZones());
timeZones.Sort(delegate(TimeZoneInfo left, TimeZoneInfo right)
{
int comparison = left.BaseUtcOffset.CompareTo(right.BaseUtcOffset);
if (comparison == 0)
{
return string.CompareOrdinal(left.DisplayName, right.DisplayName);
}
return comparison;
});

This will give you alphabetical sorts for time zones with the same base UTC offset, and your results should match the built-in Windows time zone list exactly.

Whitney Kew

By: daniella

daniella — Tue, 05 Feb 2008 15:20:35 +0000

Hi again! Yesterday You saved me the day!!!

By: Tatham Oddie

Tatham Oddie — Mon, 04 Feb 2008 23:38:43 +0000

Hi Daniella,

I have updated the post with a VB.NET version.

Tatham

By: daniella

daniella — Mon, 04 Feb 2008 23:34:10 +0000

Thanks a lot!! I’ll test it now!!

By: daniella

daniella — Mon, 04 Feb 2008 21:59:19 +0000

I have the same problem but I work in VB and I have no matter to trasnlate it to VB… May somebody help me?!