feat: add timezone support to scheduling for Lambda functions #3016

fossamagna · 2025-10-06T14:24:20Z

Problem

Function schedules are powered by Amazon EventBridge rules, so not supported timezone.
Migrate EventBridge Scheduler to support timezone.

Issue number, if available:

fix #3008

Changes

Added a function schedule format that specifies the timezone.
We migrated from EventBridge rules to EventBridge Scheduler to support time zones.

Corresponding docs PR, if applicable:

aws-amplify/docs#8448

Validation

Checklist

If this PR includes a functional change to the runtime behavior of the code, I have added or updated automated test coverage for this change.
If this PR requires a change to the Project Architecture README, I have included that update in this PR.
If this PR requires a docs update, I have linked to that docs PR above.
If this PR modifies E2E tests, makes changes to resource provisioning, or makes SDK calls, I have run the PR checks with the run-e2e label set.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

changeset-bot · 2025-10-06T14:24:24Z

🦋 Changeset detected

Latest commit: 2debf5a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@aws-amplify/backend-function	Minor
@aws-amplify/backend	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

iankhou

Thanks for the contribution, added some comments.

iankhou · 2025-10-07T20:29:35Z

packages/backend-function/src/schedule_parser.ts

+  } else if ('cron' in schedule) {
+    return { ...schedule, timezone: schedule.timezone ?? DEFAULT_TIMEZONE };
+  }
+  throw new Error("Could not determine the function's schedule type");


This Error is not tested, can you include a test that covers it?

iankhou · 2025-10-07T20:35:27Z

packages/backend-function/src/factory.test.ts

+      });
+    });
+
+    void it('sets valid schedule - rate with timezone', () => {


Could you add some test cases for invalid inputs for rate and timezone (invalid timezone)?

iankhou · 2025-10-07T21:14:39Z

One of our workflows is failing because the changeset bumps @aws-amplify/backend-function but not @aws-amplify/backend. It needs to bump both, as @aws-amplify/backend-function can't be higher than @aws-amplify/backend.

iankhou · 2025-10-07T21:17:02Z

.changeset/ready-cities-wonder.md

@@ -0,0 +1,5 @@
+---
+'@aws-amplify/backend-function': minor


Need to bump @aws-amplify/backend too.

fossamagna · 2025-10-08T00:27:39Z

@iankhou
Thank you for your review.
I have addressed the comments you suggested.

iankhou

One thing, we should use TimeZone instead of string timezones, unless there is a very good reason not to.

iankhou · 2025-10-08T14:49:05Z

packages/backend-function/src/schedule_parser.ts

+  CronOptionsWithTimezone,
+  ScheduleExpression,
+} from 'aws-cdk-lib/aws-scheduler';
+import { TimeZone } from 'aws-cdk-lib';


I see we are importing TimeZone here, why do we use string timezones in the rest of the changes?

iankhou · 2025-10-08T14:49:39Z

packages/backend-function/src/schedule_parser.ts

-        return { minute: `*/${value}` };
+        return {
+          minute: `*/${value}`,
+          timeZone: TimeZone.of(schedule.timezone),


Why not pass a TimeZone directly instead of making this conversion?

iankhou · 2025-10-08T14:50:19Z

packages/backend-function/API.md

+    timezone: string;
+};
+
+// @public (undocumented)
+export type ZonedTimeInterval = {
+    rate: TimeIntervalExpression;
+    timezone: string;


Same as comments above - TimeZone

fossamagna · 2025-10-09T00:32:38Z

@iankhou
I noticed that none of the properties in FunctionProps use CDK types, so I assumed this was an intentional design choice.
Following this pattern, I chose to use the string type for FunctionSchedule.timezone instead of the CDK TimeZone.
If my assumption is incorrect, please let me know. I'd be happy to change it back to use the CDK TimeZone type.

iankhou · 2025-10-09T15:15:36Z

Not sure if that is intentional. I will consult with the team and get back to you soon.

Some additional info -

Did some research on this implementation and came away with the following findings:

Case 1: Your approach of:

timeZone: TimeZone.of(schedule.timezone),

fails an SDK call at deploy time when the timezone is invalid - which is good.

Case 2: An alternate approach of:

timeZone: schedule.timezone as unknown as TimeZone,

does not fail deployment, and defaults to UTC

I had been worried that your implementation may fall victim to Case 2, but it does not.

Still, would be best if we catch problems with the timezone at compile time.

iankhou

Looks like we do have the precedence of using strings for these props.

Using strings instead of CDK types here makes configuration easier in some cases. I will approve this PR as-is.

Thanks @ShadowCat567 for confirming this, and thank you for your patience!

fossamagna · 2025-10-10T00:36:14Z

@iankhou Thank you for your prompt and polite response.

feat: add timezone support to scheduling for Lambda functions

3c84b8a

fossamagna mentioned this pull request Oct 6, 2025

feat(function): add timezone support for scheduling function aws-amplify/docs#8448

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fossamagna marked this pull request as ready for review October 6, 2025 15:00

fossamagna requested review from a team as code owners October 6, 2025 15:00

iankhou requested changes Oct 7, 2025

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Merge branch 'main' into schedule-timezone

c0e963a

iankhou reviewed Oct 7, 2025

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fossamagna added 3 commits October 8, 2025 09:10

test: add validation for invalid schedule format in ScheduleParser

ee33609

test: add tests for handling invalid timezones in schedule property

9396320

chore: bump '@aws-amplify/backend' version

2debf5a

fossamagna requested a review from iankhou October 8, 2025 00:27

jiayiwang7 assigned iankhou Oct 8, 2025

iankhou requested changes Oct 8, 2025

View reviewed changes

iankhou added the feature-request New feature or request label Oct 8, 2025

iankhou approved these changes Oct 9, 2025

View reviewed changes

ShadowCat567 approved these changes Oct 9, 2025

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iankhou merged commit 603e831 into aws-amplify:main Oct 9, 2025
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feat: add timezone support to scheduling for Lambda functions #3016

feat: add timezone support to scheduling for Lambda functions #3016

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