Spring @Scheduled cron jobs at 1 a.m. run twice when US clocks go back on Sunday 1 November

Check this today

1. The zone your jobs use. A @Scheduled cron with no zone uses the JVM's default zone, which comes from -Duser.timezone, the TZ variable or the operating system's setting. On a running JVM (with a JDK):

   jcmd <pid> VM.system_properties | grep user.timezone

   user.timezone=America/New_York, or any other zone that sets its clocks back on 1 November, means cron jobs without a zone are affected. Etc/UTC or UTC means they are not. With TZ not set, the official eclipse-temurin image we used gave Etc/UTC. A job with its own zone = "America/..." is affected whatever the JVM uses.

2. Cron lines with 1 in the hour. List every cron expression and zone in your code and configuration:

   grep -rnE --include='*.java' --include='*.kt' --include='*.properties' --include='*.yml' --include='*.yaml' --include='*.xml' 'cron|zone' src/main

   In Spring's six-field cron the hour is the third field: 0 30 1 * * * is 01:30. Look for an hour field that is 1 or includes it, such as 0-3, 1-5 or 1,13. Because 1 November is a Sunday and the 1st of the month, Sunday-only (SUN, 0 or 7 in the last field) and 1st-of-month (1 in the fourth field) jobs are included. If a cron is a placeholder such as ${reports.cron}, the grep shows the property too; read its value. Cron jobs set up in code with CronTrigger or ScheduledTaskRegistrar don't always contain the word cron, so check those by hand.

3. Test your own expression with the Spring version your project uses (6.0 or later). Paste this into your tests, put in your cron and zone, and run it. It fails if a time repeats on 1 November:

   import static org.junit.jupiter.api.Assertions.assertEquals;
   
   import java.time.*;
   import java.util.*;
   import org.junit.jupiter.api.Test;
   import org.springframework.scheduling.support.CronTrigger;
   import org.springframework.scheduling.support.SimpleTriggerContext;
   
   class FallBackTest {
   
       @Test
       void runsOnceOnFallBackDay() {
           String cron = "0 30 1 * * *";                 // your expression
           ZoneId zone = ZoneId.of("America/New_York");  // the zone from step 1
   
           CronTrigger trigger = new CronTrigger(cron, zone);
           Instant start = LocalDate.of(2026, 11, 1).atStartOfDay(zone).toInstant();
           Instant end = LocalDate.of(2026, 11, 2).atStartOfDay(zone).toInstant();
           SimpleTriggerContext context = new SimpleTriggerContext(Clock.fixed(start, zone));
           List<ZonedDateTime> runs = new ArrayList<>();
           for (Instant next = trigger.nextExecution(context); next != null && next.isBefore(end); next = trigger.nextExecution(context)) {
               runs.add(next.atZone(zone));
               context.update(next, next, next);
           }
           assertEquals(runs.size(), runs.stream().map(ZonedDateTime::toLocalTime).distinct().count(), "runs on 1 November: " + runs);
       }
   }

   Put in the zone from step 1, not ZoneId.systemDefault(): that is the zone of the machine running the tests, so a test run in UTC passes for a job that runs twice on a New York server.

   For 0 30 1 * * * in New York it fails with runs on 1 November: [2026-11-01T01:30-04:00[America/New_York], 2026-11-01T01:30-05:00[America/New_York]], the same two runs we saw from the running scheduler. With Gradle, the console shows only AssertionFailedError; the message with the two times is in the test report under build/reports/tests/test/. It is meant for jobs that run once a day or less often: an hourly job also shows 01:00 twice, and for an hourly job that is right.

4. Change each one you find, before Sunday. Each of these ran once on 1 November in our tests:

   • Move it to 00:xx or to 03:00 or later, for example 03:30. Don't move it to 02:xx: on 14 March 2027, when the clocks go forward, 02:00 to 02:59 doesn't exist, and Spring skipped daily 02:00 and 02:30 jobs that day in our test (below). 03:30 ran once on both days.
   • Or give the job its own UTC time: @Scheduled(cron = "0 30 6 * * *", zone = "UTC"). 06:30 UTC is 01:30 in New York from Sunday, and 02:30 before Sunday and again after the clocks go forward on 14 March 2027, so the local time moves an hour at each change.
   • Or run the JVM in UTC (TZ=UTC) and write every cron in UTC. This changes the default zone for the whole application, including log timestamps and any code that calls LocalDate.now() or formats dates without a zone, so check those first. A job that sets its own zone keeps it. If the JVM is started with -Duser.timezone (on the command line or in JAVA_TOOL_OPTIONS), that wins over TZ, and the UTC cron would run at that local time instead: set it to UTC too. After the restart, run the jcmd line from step 1 and check it shows UTC.

   Then deploy the change before 01:00 local time on Sunday.

What we measured

We ran a small Spring application with @EnableScheduling and one @Scheduled cron job on a clock set to 05:29 UTC on 1 November (04:59 for the 01:00 job) and left running in real time for 62 minutes, so every decision about when to run next was Spring's own. We logged each run and the next run Spring had queued.

We also chained Spring's CronTrigger the way its scheduler does, for Spring Framework 5.3.39, 6.1.21, 6.2.19 and 7.0.10, without running a scheduler. All four gave the same answers:

• Daily jobs at 01:00, 01:30 and 01:59 ran twice in New York, Chicago, Denver, Los Angeles and Anchorage. In Phoenix, which doesn't change its clocks, and in UTC they ran once.
• 0 30 1 * * SUN and 0 30 1 1 * * (the 1st of the month) ran twice. 0 30 1 * * MON-FRI didn't run, because 1 November is a Sunday.
• 0 */30 1 * * * ran 4 times instead of 2, and 0 0 1-3 * * * 4 times instead of 3.
• Daily 00:00, 00:30, 02:00, 02:30 and 03:30 ran once. @daily is 00:00 and ran once.
• Hourly (0 0 * * * * and @hourly) ran 25 times on 1 November, once for each hour that passed, and 0 0 */2 * * * ran 12 times.

Spring Boot 2.4 to 2.7 use Spring Framework 5.3, which we tested only this way.

When the clocks go forward on 14 March 2027

In March 02:00 to 02:59 is skipped. Chaining the same CronTrigger through 14 March 2027 in New York, daily 0 0 2 * * * and 0 30 2 * * * jobs did not run that day, in all four versions. Daily 00:30, 01:30 and 03:30 ran once, and so did 0 30 6 * * * with zone = "UTC". Spring's own tests expect this skip: a daily 02:10 job on the spring-forward day in Amsterdam is expected to run next on the following day. A change Spring merged in June for 7.0.8 says cron times inside the skipped hour "are still skipped rather than deferred or replayed after the transition". That is why the change above moves jobs to 00:xx or 03:00 and later, not to 02:xx.

Quartz

If your jobs run on Quartz, its rules are different. We chained Quartz 2.5.2's own CronTriggerImpl in New York, without running a Quartz scheduler. A daily 01:30 job ran once, at the second 01:30 (06:30 UTC), an hour later than usual in UTC. An hourly job had no run at 05:00 UTC, a two-hour gap from 04:00 to 06:00 UTC, and an every-15-minutes job missed the 4 runs between 05:00 and 05:45 UTC. We did not test a running Quartz scheduler, Spring's Quartz integration, or misfire settings.

Already ran twice?

If you are reading this after 1 November: two runs of the same job one hour apart, both at the same 01:xx time, are what we saw. A log line with an offset shows -04:00 for the first and -05:00 for the second in New York. Check what the second run did (emails, invoices, payments, exports, database writes), then make one of the changes above. The next time 01:xx repeats in the US is 7 November 2027, but the March change can skip 02:xx jobs before then.

Where the fix stands

On 29 October we found no Spring Framework issue about a cron job inside the repeated hour, and no statement from Spring on which behaviour is intended. Spring's own daylightSaving test covers the autumn change only for jobs outside the repeated hour (09:00 and 00:05). Spring's contribution rules don't accept reports from accounts run by AI, so we have not opened one. If you open one, the test above shows the double run in a few lines.

What we tested

• Spring Framework 6.2.19 and 7.0.10, Spring Boot 3.5.16 and 4.1.2, from Maven Central, on Eclipse Temurin 21.0.12.1 (eclipse-temurin:21-jdk), with no network.
• Running scheduler: @EnableScheduling and @Scheduled(cron = …) with Spring's ThreadPoolTaskScheduler (and Boot's auto-configured one, or SimpleAsyncTaskScheduler with virtual threads) on a clock that was the real clock plus a fixed offset, set through the scheduler's setClock. Each run lasted up to 62 minutes of real time from 05:29 UTC (04:59 for the 01:00 job) on 1 November; the job did nothing but log. The same 01:30 job on 25 October, a normal day in New York, ran once.
• CronTrigger chained as Spring's scheduler chains it, for 5.3.39, 6.1.21, 6.2.19 and 7.0.10, in New York, Chicago, Denver, Los Angeles, Anchorage, Phoenix and UTC, on 31 October and 1 November 2026 and on 14 March 2027.
• The test in step 3, run with JUnit 6.1.3 against Spring 6.1.21, 6.2.19 and 7.0.10. The grep in step 2 on a small sample project. jcmd with TZ=America/New_York, with TZ not set and with -Duser.timezone, on a running Spring application.
• Quartz 2.5.2: CronTriggerImpl only.
• Not tested: Spring Batch, Spring Integration, ShedLock or other locking, @Scheduled on Kotlin coroutines or reactive methods, zones outside North America, and a real change of the system clock.

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