RFR: 8299194: CustomTzIDCheckDST.java may fail at future date

Ichiroh Takiguchi itakiguchi at openjdk.org
Wed Dec 21 16:05:25 UTC 2022 

test/jdk/java/util/TimeZone/CustomTzIDCheckDST.java may fail at future date.
I used following standalone testcase

import java.util.Calendar;
import java.util.Date;
import java.util.SimpleTimeZone;

public class CheckDST {
    private static String CUSTOM_TZ = "MEZ-1MESZ,M3.5.0,M10.5.0";
    public static void main(String args[]) throws Throwable {
        runTZTest();
    }

    /* TZ code will always be set to "MEZ-1MESZ,M3.5.0,M10.5.0".
     * This ensures the transition periods for Daylights Savings should be at March's last
     * Sunday and October's last Sunday.
     */
    private static void runTZTest() {
        Date time = new Date();
        if (new SimpleTimeZone(3600000, "MEZ-1MESZ", Calendar.MARCH, -1, Calendar.SUNDAY, 0,
                Calendar.OCTOBER, -1, Calendar.SUNDAY, 0).inDaylightTime(time)) {
            // We are in Daylight savings period.
            if (time.toString().endsWith("GMT+02:00 " + Integer.toString(time.getYear() + 1900)))
                return;
        } else {
            if (time.toString().endsWith("GMT+01:00 " + Integer.toString(time.getYear() + 1900)))
                return;
        }

        // Reaching here means time zone did not match up as expected.
        throw new RuntimeException("Got unexpected timezone information: " + time);
    }
}


I tested CheckDST with faketime, then I got following results

$ TZ=GMT faketime -m "2023-03-25 22:59:59" env TZ="MEZ-1MESZ,M3.5.0,M10.5.0" $HOME/jdk-21-b02/bin/java CheckDST
$ TZ=GMT faketime -m "2023-03-25 23:00:00" env TZ="MEZ-1MESZ,M3.5.0,M10.5.0" $HOME/jdk-21-b02/bin/java CheckDST
Exception in thread "main" java.lang.RuntimeException: Got unexpected timezone information: Sun Mar 26 00:00:00 GMT+01:00 2023
        at CheckDST.runTZTest(CheckDST.java:28)
        at CheckDST.main(CheckDST.java:8)


I assume `TZ=MEZ-1MESZ`refers Europe/Berlin timezone.
In this case, `TZ` environment variable should be `MEZ-1MESZ,M3.5.0,M10.5.0/3` (`/3` is missing in testcase)

CustomTzIDCheckDST should run with daylight saving time.
Add Simulate Southern Hemisphere by `MEZ-1MESZ,M10.5.0,M3.5.0/3`

Tested by standalone testcase

$ cat CheckDST1.java
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.util.SimpleTimeZone;
import java.util.TimeZone;
import java.time.DayOfWeek;
import java.time.ZonedDateTime;
import java.time.temporal.TemporalAdjusters;
public class CheckDST1 {
    // Northern Hemisphere
    private static String CUSTOM_TZ = "MEZ-1MESZ,M3.5.0,M10.5.0/3";
    // Simulate Southern Hemisphere
    private static String CUSTOM_TZ2 = "MEZ-1MESZ,M10.5.0,M3.5.0/3";
    public static void main(String args[]) throws Throwable {
        runTZTest();
    }

    /* TZ code will always be set to "MEZ-1MESZ,M3.5.0,M10.5.0/3".
     * This ensures the transition periods for Daylights Savings should be at March's last
     * Sunday and October's last Sunday.
     */
    private static void runTZTest() {
        Date time = new Date();
        String tzStr = System.getenv("TZ");
        if (tzStr == null)
            throw new RuntimeException("Got unexpected timezone information: TZ is null");
        boolean nor = tzStr.matches(".*,M3\..*,M10\..*");
        TimeZone tz = new SimpleTimeZone(3600000, tzStr,
            nor ? Calendar.MARCH : Calendar.OCTOBER, -1,
            Calendar.SUNDAY, 3600000, SimpleTimeZone.UTC_TIME,
            nor ? Calendar.OCTOBER : Calendar.MARCH, -1,
            Calendar.SUNDAY, 3600000, SimpleTimeZone.UTC_TIME,
            3600000);
        System.out.println(time);
        if (tz.inDaylightTime(time)) {
            // We are in Daylight savings period.
            if (time.toString().endsWith("GMT+02:00 " + Integer.toString(time.getYear() + 1900)))
                return;
        } else {
            if (time.toString().endsWith("GMT+01:00 " + Integer.toString(time.getYear() + 1900)))
                return;
        }

        // Reaching here means time zone did not match up as expected.
        throw new RuntimeException("Got unexpected timezone information: " + tzStr + " " + time);
    }

    private static ZonedDateTime getLastSundayOfMonth(ZonedDateTime date) {
        return date.with(TemporalAdjusters.lastInMonth(DayOfWeek.SUNDAY));
    }
}


Check Europe/Berlin timezone settings

$ zdump -v Europe/Berlin | grep 2023
Europe/Berlin  Sun Mar 26 00:59:59 2023 UTC = Sun Mar 26 01:59:59 2023 CET isdst=0 gmtoff=3600
Europe/Berlin  Sun Mar 26 01:00:00 2023 UTC = Sun Mar 26 03:00:00 2023 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Oct 29 00:59:59 2023 UTC = Sun Oct 29 02:59:59 2023 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Oct 29 01:00:00 2023 UTC = Sun Oct 29 02:00:00 2023 CET isdst=0 gmtoff=3600


Test results are as follows:

Northern Hemisphere side

$ TZ=GMT faketime -m '2023-03-26 00:59:59' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 date
Sun Mar 26 01:59:59 MEZ 2023
$ TZ=GMT faketime -m '2023-03-26 00:59:59' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 java CheckDST1
Sun Mar 26 01:59:59 GMT+01:00 2023

$ TZ=GMT faketime -m '2023-03-26 01:00:00' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 date
Sun Mar 26 03:00:00 MESZ 2023
$ TZ=GMT faketime -m '2023-03-26 01:00:00' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 java CheckDST1
Sun Mar 26 03:00:00 GMT+02:00 2023

$ TZ=GMT faketime -m '2023-10-29 00:59:59' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 date
Sun Oct 29 02:59:59 MESZ 2023
$ TZ=GMT faketime -m '2023-10-29 00:59:59' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 java CheckDST1
Sun Oct 29 02:59:59 GMT+02:00 2023

$ TZ=GMT faketime -m '2023-10-29 01:00:00' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 date
Sun Oct 29 02:00:00 MEZ 2023
$ TZ=GMT faketime -m '2023-10-29 01:00:00' env TZ=MEZ-1MESZ,M3.5.0,M10.5.0/3 java CheckDST1
Sun Oct 29 02:00:00 GMT+01:00 2023


Southern Hemisphere

$ TZ=GMT faketime -m '2023-03-26 00:59:59' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 date
Sun Mar 26 02:59:59 MESZ 2023
$bTZ=GMT faketime -m '2023-03-26 00:59:59' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 java CheckDST1
Sun Mar 26 02:59:59 GMT+02:00 2023

$ TZ=GMT faketime -m '2023-03-26 01:00:00' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 date
Sun Mar 26 02:00:00 MEZ 2023
$ TZ=GMT faketime -m '2023-03-26 01:00:00' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 java CheckDST1
Sun Mar 26 02:00:00 GMT+01:00 2023

$ TZ=GMT faketime -m '2023-10-29 00:59:59' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 date
Sun Oct 29 01:59:59 MEZ 2023
$ TZ=GMT faketime -m '2023-10-29 00:59:59' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 java CheckDST1
Sun Oct 29 01:59:59 GMT+01:00 2023

$ TZ=GMT faketime -m '2023-10-29 01:00:00' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 date
Sun Oct 29 03:00:00 MESZ 2023
$ TZ=GMT faketime -m '2023-10-29 01:00:00' env TZ=MEZ-1MESZ,M10.5.0,M3.5.0/3 java CheckDST1
Sun Oct 29 03:00:00 GMT+02:00 2023

-------------

Commit messages:
 - 8299194: CustomTzIDCheckDST.java may fail at future date

Changes: https://git.openjdk.org/jdk/pull/11756/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11756&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299194
  Stats: 21 lines in 1 file changed: 16 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/11756.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11756/head:pull/11756

PR: https://git.openjdk.org/jdk/pull/11756

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