Unexpected results while converting time zones on Windows Server

[R,S]

In working with time zone conversions, I ran into some unexpected results. The examples below show a couple of the anomalies. My understanding is that all of the EU changes to or from Summer time at the same time (through the end of March 2021, at least [end of time changes in EU]), so shouldn't the local time in the adjacent time zones always have offsets that are one hour apart, even on the day that the offsets change?


Here is an example in PowerShell:


$d = Get-Date '2019-10-26 20:30:00 -04:00' # Eastern Time doesn't fall back to -05:00 until November

@( [System.TimeZoneInfo]::ConvertTimeBySystemTimeZoneId($d, 'W. Europe Standard Time'), [System.TimeZoneInfo]::ConvertTimeBySystemTimeZoneId($d, 'Central Europe Standard Time'), [System.TimeZoneInfo]::ConvertTimeBySystemTimeZoneId($d, 'E. Europe Standard Time') )



(There are two lines of code there - the first one starting with "$d" and the second one starting with "@(".)





The same example in SQL Server 2017:


declare @nyTime datetimeoffset = convert(datetimeoffset, N'2019-10-26 20:30:00.000000 -04:00', 121);

select @nyTime at time zone N'W. Europe Standard Time' [W. Europe Time],
@nyTime at time zone N'Central Europe Standard Time' [Central Europe Time],
@nyTime at time zone N'E. Europe Standard Time' [E. Europe Time];








The server is running Windows Server 2016 with the February 2019 update KB4487006.

(Please do not redirect this to another forum - I already got bounced from here to the SQL Server forum - who said the time zone conversions are handled by the underlying Windows OS - to the Windows forum and back here to the Windows Server forum.)

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