The July 2019 update provides below changes for Brazil Daylight Savings Time (DST). Brazil has decided to no longer follow DST. DST won’t start on the first Sunday of November 2019 as previously s...
Updated Mar 31, 2023
Version 5.0
Blog Post
Hello everybody,
For those who have issues regarding out DST changes in Brazil, I've a workaround until you/we all manage to get the right updates in our Windows 10 machines.
First, lets talk about checking our DST settings:
w32tm /tz
Running W32Time with the parameter /tz give us an outpout showing the Standard Name for the Time Zone settings current in use, as well as the Month, Day and Day of the Week for the Standard time settings. It also shows the Daylight Name and its Month, Day and Day of the Week.
For us, brazilian users, our machines should show (M:1 D:1 DoW:2) for the Brazilian DST as in the image below:
*The PowerShell script from wellersonnascimento provide us more details for this settings if you run it.
In a machine without the proper updates regarding our DST settings, the line about the Brazilian DST will show values like (M:11 D:1 DoW:6).
Now, about the workaround:
In the Windows registry, look for the entry [ HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\E. South America Standard Time\Dynamic DST ].
There we should see something like this:
And for one key up in the tree:
Both images were taken from a computer running Windows 10 with the proper DST settings. Any software that depends on the W10 DST settings and its registry entries should be fine with its time calculations, like Outlook for instance. *Check this link for a more detailed view of how Outlook handles it:
https://support.microsoft.com/en-us/help/2642044/how-time-zone-normalization-works-in-microsoft-outlook
Exporting the key E. South America Standard Time and importing it in a computer with the wrong settings is halfway there. After importing the key we should run w32tm /resync to "resync" the Time Zone settings, as the command suggests.
This workaround will work well until the affected machine receives any Windows Update containing the old DST settings. What did happen in some 1803 builds in my company... and I had to reapply the workaround until we properly updated every single machine.
* In the Outlook link that I gave you, there is no mention about how it reacts regarding the DST settings on our Exchange servers.
If anyone needs it, here goes a .reg file with all key/values we need:
Spoiler
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\E. South America Standard Time]
"Display"="(UTC-03:00) Brasília"
"Dlt"="Horário brasileiro de verão"
"MUI_Display"="@tzres.dll,-40"
"MUI_Dlt"="@tzres.dll,-41"
"MUI_Std"="@tzres.dll,-42"
"Std"="Hora oficial do Brasil"
"TZI"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,00,00,03,00,00,00,00,\
00,00,00,00,00,00,00,01,00,02,00,01,00,00,00,00,00,00,00,00,00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\E. South America Standard Time\Dynamic DST]
"2004"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,02,00,17,00,\
3b,00,3b,00,e7,03,00,00,0b,00,02,00,01,00,00,00,00,00,00,00,00,00
"2005"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,00,00,03,00,00,00,00,00,00,00,00,00
"2006"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0b,00,00,00,01,00,00,00,00,00,00,00,00,00
"2007"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,05,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,00,00,02,00,00,00,00,00,00,00,00,00
"2008"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,00,00,03,00,00,00,00,00,00,00,00,00
"2009"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,02,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2010"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2011"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2012"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,04,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2013"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2014"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2015"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2016"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,03,00,17,00,3b,00,3b,00,e7,03
"2017"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0a,00,06,00,02,00,17,00,3b,00,3b,00,e7,03
"2018"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,06,00,03,00,17,00,\
3b,00,3b,00,e7,03,00,00,0b,00,06,00,01,00,17,00,3b,00,3b,00,e7,03
"2019"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,02,00,00,00,03,00,00,00,\
00,00,00,00,00,00,00,00,01,00,02,00,01,00,00,00,00,00,00,00,00,00
"2020"=hex:b4,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"FirstEntry"=dword:000007d4
"LastEntry"=dword:000007e4
I hope to be of help!
Best Regards,
Daniel Lima