![]() ![]() The Dynamic DST entries support the Win32 DYNAMIC_TIME_ZONE_INFORMATION structure, and corresponding APIs with "dynamic" in their name, such as GetDynamicTimeZoneInformation. (click the image to see the full resolution, and note the areas I manually marked in red that change year-over-year) ![]() But in the case of Brazil, you'll notice Dynamic DST entries for 2009 through 2040. For some time zones, this isn't necessary at all, and for other time zones you'll find a very small amount of data because the same rule repeats year after year. If you expand the registry entry, you'll see that there is a sub-key called "Dynamic DST" which contains the year-by-year changes to the data. South America Standard Time", the time zone data is correct. With regard to the Windows time zone you mentioned, "E. ![]() Thus, we issue interim guidance to use a different time zone for the time being, then switch back once we have data that properly reflects the full history of time in the affected region. But due to the short notice, and the time it takes to process such a change in the Windows operating system, it will be a little while before there is a new "Sudan Standard Time" time zone created in the Windows time zone data. IANA has processed this change, and so has Microsoft. In some cases we cannot because they don't offer enough lead time.Ĭonsider the recent case of Sudan, who told the the IANA tz mailing list on October 17th, 2017 of a change effective November 1st 2017. In some cases, we can meet the effective-dates established by these different governments. ![]() For example, we recently posted a notice about upcoming Windows time zone changes for Fiji, Cyprus, Sudan, Tonga, Namibia, and Turks & Caicos. There are several challenges, including the timing of time zone changes as given by governments. NOTE I'm working with Windows 7, but the issue remains the same on Windows 10Īs a Microsoft employee with significant involvement with Windows time zone data, please allow me to assure you that Microsoft works very hard to ensure that it releases updates to keep Windows time zone data as accurate as it possibly can be. I'm pretty sure that is not an error of this type. NOTE I have strongly verified if the data I read from the registry were correct before posting this message. Are timezone written in Windows registry reliable, if not, which function of the Windows API should I use to convert a timezone with DST from a date written in a different timezone than the one set on the local machine?.Is there a reason why a DST start date, that obviously occurs regularly every year, on the 3rd week of the 10th month, have a value set on the 2nd week?.Is there known issues about several timezone, especially the "E.Have I understood the recurrence rule correctly? (Here is what MSDN says about it: (v=vs.85).aspx).The description of the data content may be found here: (v=vs.85).aspx Furthermore, as you can see on the provided screenshot, the Windows registry data shows 2 weeks for the DST start time (highlighted in blue), but 3 weeks for the DST end time (surrounded in red), which is calculated correctly by my code. However this rule matches rarely with the correct date published on the internet for the time changing, whereas the dates are all correct if the rule would be "every year, on the 2nd month, on the 3nd week of the month". If I understood right, the recurrence rule returned by Windows for this specific timezone says "every year, on the 2nd month, on the 2nd week of the month". With the recurrence provided by Windows, the DST start day begins 1 week sooner. However I noticed that the day the DST should occur is sometimes incorrect on several timezone. I'm able to create a recurrence rule from the Windows info without problems. Now some timezone have also a Daylight Saving Time to consider. But in order to convert a time from another timezone to UTC, I need to get the timezone information from the Windows registry. To convert from UTC to local computer time I have several functions of the Windows API at my disposal to do the job. The event from Tokyo is first converted in UTC time, then reconverted from UTC to the computer local time in Berlin, and finally shown to the user on his graphical interface. For example, an user working in Berlin receives an event written in Tokyo. The application receives an event, with a reference timezone, and this event is shown graphically to the user at the correct hour, in his local timezone. I'm creating a c++ project that should works on several timezone. ![]()
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