Daylight saving time fix by mrm9084 · Pull Request #48363 · Azure/azure-sdk-for-java

mrm9084 · 2026-03-10T23:08:28Z

Description

Fixes an issue where timezone info doesn't work around Daylight Savings time for the recurring time filter.

All SDK Contribution checklist:

The pull request does not introduce [breaking changes]
CHANGELOG is updated for new features, bug fixes or other significant changes.
I have read the contribution guidelines.

General Guidelines and Best Practices

Title of the pull request is clear and informative.
There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

Pull request includes test coverage for the included changes.

Copilot

Pull request overview

This PR addresses a Daylight Saving Time (DST) issue in the Spring Cloud Azure Feature Management “recurring time window” logic, aiming to make recurrence validation/evaluation behave consistently across DST transitions.

Changes:

Update recurrence validation to use UTC when computing week-based gaps (avoids DST-dependent day lengths).
Add DST-focused unit tests for RecurrenceValidator and RecurrenceEvaluator.
Add DST-handling logic in weekly recurrence evaluation when comparing fixed-offset start times with region-based “now” times.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
`sdk/spring/spring-cloud-azure-feature-management/src/main/java/com/azure/spring/cloud/feature/management/implementation/timewindow/recurrence/RecurrenceValidator.java`	Switches “today” computation to UTC to avoid DST affecting duration/gap calculations.
`sdk/spring/spring-cloud-azure-feature-management/src/main/java/com/azure/spring/cloud/feature/management/implementation/timewindow/recurrence/RecurrenceEvaluator.java`	Adds DST-aware zone conversion logic for weekly recurrence computations.
`sdk/spring/spring-cloud-azure-feature-management/src/test/java/com/azure/spring/cloud/feature/management/filters/recurrence/RecurrenceValidatorDSTTest.java`	Introduces DST-related validation tests (currently mostly “no exception” assertions).
`sdk/spring/spring-cloud-azure-feature-management/src/test/java/com/azure/spring/cloud/feature/management/filters/recurrence/RecurrenceEvaluatorDSTTest.java`	Introduces DST-related evaluation tests for fixed-offset vs region-zone comparisons.

...com/azure/spring/cloud/feature/management/filters/recurrence/RecurrenceEvaluatorDSTTest.java

Copilot · 2026-03-10T23:13:17Z

...com/azure/spring/cloud/feature/management/filters/recurrence/RecurrenceValidatorDSTTest.java

+    /**
+     * Test that validator uses UTC for today's date calculation.
+     * This ensures consistency regardless of the system's default timezone
+     * or DST transitions.
+     */
+    @Test
+    public void validateSettingsUsesUTCForDateCalculation() {
+        final TimeWindowFilterSettings settings = new TimeWindowFilterSettings();
+        final RecurrencePattern pattern = new RecurrencePattern();
+        final RecurrenceRange range = new RecurrenceRange();
+        final Recurrence recurrence = new Recurrence();
+
+        pattern.setType("Weekly");
+        pattern.setDaysOfWeek(List.of("Monday", "Wednesday", "Friday"));
+        pattern.setFirstDayOfWeek("Monday");
+        pattern.setInterval(1);
+
+        recurrence.setRange(range);
+        recurrence.setPattern(pattern);
+
+        // Start on a Monday
+        settings.setStart("2024-03-04T10:00:00+01:00"); // Monday
+        settings.setEnd("2024-03-04T12:00:00+01:00");
+        settings.setRecurrence(recurrence);
+
+        // Should not throw exception, uses UTC internally for validation
+        assertDoesNotThrow(() -> RecurrenceValidator.validateSettings(settings),
+            "Validator should use UTC and not throw exception");
+    }


These validator DST tests currently only assert that validateSettings doesn’t throw for very short windows (1–2 hours). That will pass regardless of whether the DST gap is treated as 23/24/25 hours, so it doesn’t actually validate the UTC/DST fix.

To make this test meaningful, use a window duration close to the minimum day gap (e.g., between 23h and 24h) and drive the reference “today/week” used by isDurationCompliantWithDaysOfWeek deterministically (e.g., by refactoring the validator to accept a Clock/reference ZonedDateTime for testing).

Copilot · 2026-03-10T23:13:17Z

...pring/cloud/feature/management/implementation/timewindow/recurrence/RecurrenceEvaluator.java

        final long numberOfInterval = Duration.between(firstDayOfFirstWeek, now).toSeconds()
            / Duration.ofDays((long) interval * RecurrenceConstants.DAYS_PER_WEEK).toSeconds();
-        final ZonedDateTime firstDayOfMostRecentOccurringWeek = firstDayOfFirstWeek.plusDays(
+        ZonedDateTime firstDayOfMostRecentOccurringWeek = firstDayOfFirstWeek.plusDays(
            numberOfInterval * (interval * RecurrenceConstants.DAYS_PER_WEEK));
+


numberOfInterval is computed using Duration.between(...).toSeconds() / Duration.ofDays(...).toSeconds(). Around DST transitions this can undercount by 1 when the local wall-clock time matches the weekly boundary but the underlying instants differ by +/-1 hour (e.g., 3 weeks minus 1 hour after spring-forward). This means the “most recent occurring week” can be shifted back a week, which defeats the DST fix.

Consider computing the interval count using calendar-based units (e.g., ChronoUnit.DAYS/WEEKS between LocalDates after aligning now/firstDayOfFirstWeek to the same intended zone), instead of seconds-based duration division.

...com/azure/spring/cloud/feature/management/filters/recurrence/RecurrenceEvaluatorDSTTest.java

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

Copilot · 2026-03-11T01:37:42Z

...pring/cloud/feature/management/implementation/timewindow/recurrence/RecurrenceEvaluator.java

        final long numberOfInterval = Duration.between(firstDayOfFirstWeek, now).toSeconds()
            / Duration.ofDays((long) interval * RecurrenceConstants.DAYS_PER_WEEK).toSeconds();
-        final ZonedDateTime firstDayOfMostRecentOccurringWeek = firstDayOfFirstWeek.plusDays(
+        ZonedDateTime firstDayOfMostRecentOccurringWeek = firstDayOfFirstWeek.plusDays(
            numberOfInterval * (interval * RecurrenceConstants.DAYS_PER_WEEK));
+


numberOfInterval is computed using Duration.between(...).toSeconds() / Duration.ofDays(...).toSeconds(), which is DST-sensitive when start is a fixed ZoneOffset but now is a region-based ZoneId. Across a spring-forward transition, the elapsed seconds for an exact N-week boundary can be 1 hour short, causing an off-by-one interval (and a wrong previous occurrence) even after the later zone conversion. Consider basing the interval calculation on calendar weeks/dates in the chosen evaluation zone (e.g., normalize to the target zone first, then use ChronoUnit.WEEKS/ChronoUnit.DAYS on LocalDate) and apply the same approach to the daily path too (it has the same seconds-per-day division issue).

...com/azure/spring/cloud/feature/management/filters/recurrence/RecurrenceEvaluatorDSTTest.java

Copilot · 2026-03-11T01:37:42Z

...pring/cloud/feature/management/implementation/timewindow/recurrence/RecurrenceEvaluator.java

+        // Handle DST transitions: If the calculated week start has a fixed offset (ZoneOffset)
+        // and 'now' has a region zone, check if they represent the same geographic location.
+        // We do this by checking if the fixed offset matches what the region zone's offset
+        // was at the *original start time*. If it matches, they're in the same timezone,
+        // and we should convert to the region zone for DST-aware comparisons.
+        if (firstDayOfMostRecentOccurringWeek.getZone() instanceof ZoneOffset 
+            && !(now.getZone() instanceof ZoneOffset)) {
+            // Check if the fixed offset matches the region zone's offset at the *start* instant
+            // (not at firstDayOfMostRecentOccurringWeek's instant, which might have crossed DST)
+            ZoneOffset offsetAtStart = now.getZone().getRules().getOffset(start.toInstant());
+            if (start.getOffset().equals(offsetAtStart)) {
+                // Same geographic location, convert to region zone for DST-aware comparisons
+                firstDayOfMostRecentOccurringWeek = firstDayOfMostRecentOccurringWeek
+                    .withZoneSameLocal(now.getZone());
+            }
+        }


The PR description/checklist indicates the module CHANGELOG hasn’t been updated. Since this PR fixes a customer-visible DST bug in recurrence evaluation/validation, please add an entry under “## 7.1.0-beta.1 (Unreleased) -> Bugs Fixed” in sdk/spring/spring-cloud-azure-feature-management/CHANGELOG.md.

mrm9084 added 3 commits March 10, 2026 11:04

Daylight saving time fix

0bc168c

dst tests

5a8e583

test updates

371b2b9

mrm9084 requested review from Netyyyy, avanigupta, moarychan and rossgrambo as code owners March 10, 2026 23:08

Copilot AI review requested due to automatic review settings March 10, 2026 23:08

mrm9084 requested review from a team, nroutray, rujche and saragluna as code owners March 10, 2026 23:08

github-actions bot added the azure-spring All azure-spring related issues label Mar 10, 2026

Copilot started reviewing on behalf of mrm9084 March 10, 2026 23:09 View session

Copilot AI reviewed Mar 10, 2026

View reviewed changes

Update RecurrenceEvaluator.java

bdfde03

rujche requested a review from Copilot March 11, 2026 01:31

Copilot started reviewing on behalf of rujche March 11, 2026 01:33 View session

Copilot AI reviewed Mar 11, 2026

View reviewed changes

mrm9084 added 2 commits March 11, 2026 09:29

test update

1a52d1e

Merge branch 'main' into DaylightSavingTimeFix

c9246a3

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Daylight saving time fix#48363

Daylight saving time fix#48363
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mrm9084 commented Mar 10, 2026

Description

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