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[Mobile] DateTime.Now returns incorrect local time for one hour after entering DST in 39 locales. #16395

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jgold6 opened this issue Aug 21, 2019 · 5 comments · Fixed by #16430
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@jgold6 jgold6 commented Aug 21, 2019

Steps to Reproduce

  1. Open the attached test project
  2. Set the device time on your target device to 3/8/2020 2:00 AM Central Standard Time. Note that it jumps to 3:00 AM as there is no 2:00 AM on 3/8/2020.
    If deploying to a simulator, you will have to set the time on the host workstation to set the system time for an emulator or simulator, whether iOS or Android. depending on the device/workstation, you may not be able to directly select Central Standard Time for the time zone, but may have to select, e.g. Kansas City, MO. Worth noting is that CST in Canada works correctly, and it is only CST in the US where this issue occurs, along with 38 other locales noted below.
  3. Deploy the test app to your target device.
  4. Observe the time in the app UI compared to the system time in the device status bar.

DateTimeNowDSTTest.zip

Current Behavior

Time shown is one hour earlier than is shown by the system time.

Expected Behavior

Time shown in the app matches the system time in the system status bar.

Notes

Although this issue only occurs on Xamarin.iOS and Xamarin.Android, it is a mono issue.
I reported this issue against Xam.iOS and Xam.Android in two DevDiv reports (958935 and 958936), and an iOS engineer (@mandel-macaque ) confirmed this is a mono issue and believes he identified the problem area. Thus I am opening this new issue against Mono and will be closing the DevDiv issues against XI and XA.
This issue has been reported for other locales and DST change times/dates in this closed mono issue:
#9664
Initially the above issue was about 2019 Spring and Fall changeovers. The Fall 2019 DST changeover seems to be correct, but I still notice issues for Spring 2020 as noted below.

Affected locales and details of when changeover is supposed to occur for each locale:

Cuba, Havana (Cuba Standard Time):    Jumps ahead at 12:00 AM on 3/8/2020 to 1:00 AM
US, Kansas City, MO (US Central Time):    Jumps ahead at 2:00 AM on 3/8/2020 to 3:00 AM
Anchorage, AK (Alaska Time):    Jumps ahead at 2:00 AM on 3/8/2020 to 3:00 AM
Azores ST (Ponta Delgada, Portugal):    Jumps ahead at 12:00 AM on 3/29/2020 to 1:00 AM
Iran, Tehran (Iran ST):    Jumps ahead at 12:00 AM on 3/21/2020 to 1:00 AM
Israel, Jerusalem (Israel ST):    Jumps ahead at 2:00 AM on 3/27/2020 to 3:00 AM
Jordan, Amman (Eastern European ST):    Jumps ahead at 12:00 AM on 3/27/2020 to 1:00 AM
Albania, Tirana (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Austria, Vienna (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Belgium, Brussels (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Bulgaria, Sofia (Eastern European ST):    Jumps ahead at 3:00 AM on 3/29/2020 to 4:00 AM
Czechia, Prague (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Denmark, Copenhagen (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Estonia, Tallinn (Eastern European ST):    Jumps ahead at 3:00 AM on 3/29/2020 to 4:00 AM
France, Paris (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Germany, Berlin (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Greece, Athens (Eastern European ST):    Jumps ahead at 3:00 AM on 3/29/2020 to 4:00 AM
Guernsey (UK) - cannot find in macOS time zone settings - tested only in Android:    Jumps ahead at 1:00 AM on 3/29/2020 to 2:00 AM
Holy See, Vatican City (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Hungary, Budapest (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Ireland, Dublin (Greenwich Mean Time -> Irish Standard Time):    Jumps ahead at 1:00 AM on 3/29/2020 to 2:00 AM
UK, Douglas, Isle of Man (GMT+1:00):    Jumps ahead at 1:00 AM on 3/29/2020 to 2:00 AM
Italy, Rome (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Jersey (UK) - cannot find in macOS time zone settings - tested only in Android:    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Latvia, Riga (Eastern European ST):    Jumps ahead at 3:00 AM on 3/29/2020 to 4:00 AM
Lithuania, Vilnius (Eastern European ST):    Jumps ahead at 3:00 AM on 3/29/2020 to 4:00 AM
Luxembourg, Luxembourg (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Malta, Valletta (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Moldova, Chişinău (Eastern European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Monaco, Monaco (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Netherlands, Amsterdam (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Norway, Oslo (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Poland, Warsaw (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Portugal, Lisbon (Western European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
San Marino, San Marino (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Slovakia, Bratislava (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Spain, Madrid (Central European ST):    Jumps ahead at 2:00 AM on 3/29/2020 to 3:00 AM
Ukraine, Kiev (Eastern European ST):    Jumps ahead at 3:00 AM on 3/29/2020 to 4:00 AM
United Kingdom, London (British ST):    Jumps ahead at 1:00 AM on 3/29/2020 to 2:00 AM

On which platforms did you notice this

Issue does not occur when using Desktop Mono. See notes above.

[ ] macOS
[ ] Linux
[ ] Windows
[x] iOS
[x] Android

Version Used:

Mono 6.0.0.319
Also tested Mono 6.4.0.81

Xam.Android: Version: 9.4.1.0
Also tested: 9.5.0.27

Xamarin.iOS: Version: 12.14.0.114
Also tested: 12.16.0.5

@jgold6

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@jgold6 jgold6 commented Aug 21, 2019

There is also this old, related issue that is still open: #10014

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@steveisok steveisok commented Aug 21, 2019

@mandel-macaque When you get a chance, please share w/ @MaximLipnin what you did.

steveisok added a commit that referenced this issue Sep 24, 2019
Addresses an issue with jumping into DST for some time zones when the incorrect date-time offset is returned for date-time in UTC (which comes from DateTime.Now). The fix is to just check if the incoming date-time is in UTC.

Also added a set of tests for some time zones to verify jumping into DST in general.

Fixes #16395
steveisok pushed a commit to steveisok/mono that referenced this issue Sep 24, 2019
…incorrect date-time offset is returned for date-time in UTC (which comes from DateTime.Now). The fix is to just check if the incoming date-time is in UTC

Also I added set of tests for some time zones but they verify jumping into DST in general.

Fixes mono#16395

Backport of mono#16430
akoeplinger added a commit that referenced this issue Sep 25, 2019
There is an issue with jumping into DST for some time zones when the incorrect date-time offset is returned for date-time in UTC (which comes from DateTime.Now). The fix is to just check if the incoming date-time is in UTC
Also I added set of tests for some time zones but they verify jumping into DST in general.

Fixes #16395

Backport of #16430
steveisok pushed a commit to steveisok/mono that referenced this issue Sep 25, 2019
…incorrect date-time offset is returned for date-time in UTC (which comes from DateTime.Now). The fix is to just check if the incoming date-time is in UTC

Also I added set of tests for some time zones but they verify jumping into DST in general.

Fixes mono#16395

Backport of mono#16430
jonpryor added a commit to jonpryor/xamarin-android that referenced this issue Sep 25, 2019
Changes: mono/mono@6d40f13...c99adb9

Context: mono/mono#16395

Fix time zone issue when jumping into DST
[threads] clear small_id_key TLS when unregistering a thread
jonpryor added a commit to xamarin/xamarin-android that referenced this issue Sep 26, 2019
Changes: mono/mono@6d40f13...c99adb9

Context: mono/mono#16395

Fix time zone issue when jumping into DST
[threads] clear small_id_key TLS when unregistering a thread
akoeplinger added a commit that referenced this issue Sep 26, 2019
There is an issue with jumping into DST for some time zones when the incorrect date-time offset is returned for date-time in UTC (which comes from DateTime.Now). The fix is to just check if the incoming date-time is in UTC

Also I added set of tests for some time zones but they verify jumping into DST in general.

Fixes #16395

Backport of #16430
jonpryor added a commit to xamarin/xamarin-android that referenced this issue Sep 27, 2019
Changes: mono/mono@6d40f13...c99adb9

Context: mono/mono#16395

Fix time zone issue when jumping into DST
[threads] clear small_id_key TLS when unregistering a thread
jonpryor added a commit to xamarin/xamarin-android that referenced this issue Sep 27, 2019
jonpryor added a commit to xamarin/xamarin-android that referenced this issue Oct 1, 2019
@tetri

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@tetri tetri commented Nov 11, 2019

America/Sao_Paulo still wrong with an aborted DST change in 2019 October and November

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@steveisok steveisok commented Nov 13, 2019

@MaximLipnin Can you test this out? If confirmed, open a new issue and link to this one.

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@MaximLipnin MaximLipnin commented Nov 13, 2019

@tetri Could you share the details?

jonpryor added a commit to xamarin/xamarin-android that referenced this issue Dec 3, 2019
Changes: mono/api-snapshot@fc50bc4...45a61d9

        $ git diff --shortstat fc50bc4f...45a61d93
         22 files changed, 775 insertions(+), 474 deletions(-)

Changes: mono/cecil@a6c8f5e...a6a7f5c

        $ git diff --shortstat a6c8f5e1...a6a7f5c0
         55 files changed, 818 insertions(+), 530 deletions(-)

Changes: mono/corefx@1f87de3...49f1c45

        $ git diff --shortstat e4f7102b...49f1c453
         38 files changed, 1171 insertions(+), 419 deletions(-)

Changes: mono/linker@ebe2a1f...e8d054b

        $ git diff --shortstat ebe2a1f4...e8d054bf
         137 files changed, 5360 insertions(+), 1781 deletions(-)

Changes: mono/mono@8946e49...18920a8

        $ git diff --shortstat 8946e49a...18920a83
         1811 files changed, 47240 insertions(+), 48331 deletions(-)

Changes: xamarin/xamarin-android-api-compatibility@a61271e...50a3c52

        $ git diff --shortstat a61271e0...50a3c52d
         1 file changed, 2 insertions(+), 791 deletions(-)

Fixes: #3619

Context: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1005448
Context: https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems/edit/967582
Context: dotnet/coreclr#26370
Context: dotnet/coreclr#26479
Context: dotnet/corefx#40455
Context: dotnet/corefx#40578
Context: mono/mono#7377
Context: mono/mono#12421
Context: mono/mono#12586
Context: mono/mono#14080
Context: mono/mono#14725
Context: mono/mono#14772
Context: mono/mono#15261
Context: mono/mono#15262
Context: mono/mono#15263
Context: mono/mono#15307
Context: mono/mono#15308
Context: mono/mono#15310
Context: mono/mono#15646
Context: mono/mono#15687
Context: mono/mono#15805
Context: mono/mono#15992
Context: mono/mono#15994
Context: mono/mono#15999
Context: mono/mono#16032
Context: mono/mono#16034
Context: mono/mono#16046
Context: mono/mono#16192
Context: mono/mono#16308
Context: mono/mono#16310
Context: mono/mono#16369
Context: mono/mono#16380
Context: mono/mono#16381
Context: mono/mono#16395
Context: mono/mono#16411
Context: mono/mono#16415
Context: mono/mono#16486
Context: mono/mono#16570
Context: mono/mono#16605
Context: mono/mono#16616
Context: mono/mono#16689
Context: mono/mono#16701
Context: mono/mono#16712
Context: mono/mono#16742
Context: mono/mono#16759
Context: mono/mono#16803
Context: mono/mono#16808
Context: mono/mono#16824
Context: mono/mono#16876
Context: mono/mono#16879
Context: mono/mono#16918
Context: mono/mono#16943
Context: mono/mono#16950
Context: mono/mono#16974
Context: mono/mono#17004
Context: mono/mono#17017
Context: mono/mono#17038
Context: mono/mono#17040
Context: mono/mono#17083
Context: mono/mono#17084
Context: mono/mono#17133
Context: mono/mono#17139
Context: mono/mono#17151
Context: mono/mono#17180
Context: mono/mono#17278
Context: mono/mono#17549
Context: mono/mono#17569
Context: mono/mono#17665
Context: mono/mono#17687
Context: mono/mono#17737
Context: mono/mono#17790
Context: mono/mono#17924
Context: mono/mono#17931
Context: https://github.com/mono/mono/issues/26758
Context: https://github.com/mono/mono/issues/37913
Context: xamarin/xamarin-macios#7005
jonpryor added a commit to xamarin/xamarin-android that referenced this issue Dec 3, 2019
Changes: mono/api-snapshot@fc50bc4...45a61d9

        $ git diff --shortstat fc50bc4f...45a61d93
         22 files changed, 775 insertions(+), 474 deletions(-)

Changes: mono/cecil@a6c8f5e...a6a7f5c

        $ git diff --shortstat a6c8f5e1...a6a7f5c0
         55 files changed, 818 insertions(+), 530 deletions(-)

Changes: mono/corefx@1f87de3...49f1c45

        $ git diff --shortstat e4f7102b...49f1c453
         38 files changed, 1171 insertions(+), 419 deletions(-)

Changes: mono/linker@ebe2a1f...e8d054b

        $ git diff --shortstat ebe2a1f4...e8d054bf
         137 files changed, 5360 insertions(+), 1781 deletions(-)

Changes: mono/mono@8946e49...18920a8

        $ git diff --shortstat 8946e49a...18920a83
         1811 files changed, 47240 insertions(+), 48331 deletions(-)

Changes: xamarin/xamarin-android-api-compatibility@a61271e...50a3c52

        $ git diff --shortstat a61271e0...50a3c52d
         1 file changed, 2 insertions(+), 791 deletions(-)

Fixes: #3619

Context: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1005448
Context: https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems/edit/967582
Context: dotnet/coreclr#26370
Context: dotnet/coreclr#26479
Context: dotnet/corefx#40455
Context: dotnet/corefx#40578
Context: mono/mono#7377
Context: mono/mono#12421
Context: mono/mono#12586
Context: mono/mono#14080
Context: mono/mono#14725
Context: mono/mono#14772
Context: mono/mono#15261
Context: mono/mono#15262
Context: mono/mono#15263
Context: mono/mono#15307
Context: mono/mono#15308
Context: mono/mono#15310
Context: mono/mono#15646
Context: mono/mono#15687
Context: mono/mono#15805
Context: mono/mono#15992
Context: mono/mono#15994
Context: mono/mono#15999
Context: mono/mono#16032
Context: mono/mono#16034
Context: mono/mono#16046
Context: mono/mono#16192
Context: mono/mono#16308
Context: mono/mono#16310
Context: mono/mono#16369
Context: mono/mono#16380
Context: mono/mono#16381
Context: mono/mono#16395
Context: mono/mono#16411
Context: mono/mono#16415
Context: mono/mono#16486
Context: mono/mono#16570
Context: mono/mono#16605
Context: mono/mono#16616
Context: mono/mono#16689
Context: mono/mono#16701
Context: mono/mono#16712
Context: mono/mono#16742
Context: mono/mono#16759
Context: mono/mono#16803
Context: mono/mono#16808
Context: mono/mono#16824
Context: mono/mono#16876
Context: mono/mono#16879
Context: mono/mono#16918
Context: mono/mono#16943
Context: mono/mono#16950
Context: mono/mono#16974
Context: mono/mono#17004
Context: mono/mono#17017
Context: mono/mono#17038
Context: mono/mono#17040
Context: mono/mono#17083
Context: mono/mono#17084
Context: mono/mono#17133
Context: mono/mono#17139
Context: mono/mono#17151
Context: mono/mono#17180
Context: mono/mono#17278
Context: mono/mono#17549
Context: mono/mono#17569
Context: mono/mono#17665
Context: mono/mono#17687
Context: mono/mono#17737
Context: mono/mono#17790
Context: mono/mono#17924
Context: mono/mono#17931
Context: https://github.com/mono/mono/issues/26758
Context: https://github.com/mono/mono/issues/37913
Context: xamarin/xamarin-macios#7005
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