Add isoDateTimeSecond action for ISO 8601 local timestamps without timezone

[Copilot]

isoTimestamp requires a timezone designator and isoDateTime only validates hh:mm — there was no action for local date-time with seconds (1995-03-31T00:00:00). Adds isoDateTimeSecond to fill this gap, following the existing isoTime/isoTimeSecond naming pattern.

Library

• regex.ts — New ISO_DATE_TIME_SECOND_REGEX: yyyy-mm-ddThh:mm:ss, no fractional seconds, space separator supported (consistent with isoTimeSecond)
• actions/isoDateTimeSecond/ — IsoDateTimeSecondIssue, IsoDateTimeSecondAction interfaces; two overloads (no-message / with-message); exported from actions/index.ts

Website

• API docs for isoDateTimeSecond, IsoDateTimeSecondAction, IsoDateTimeSecondIssue
• menu.md — three alphabetically-ordered entries added
• pipelines/index.mdx — isoDateTimeSecond added to validation actions ApiList

Usage

const LocalTimestampSchema = v.pipe(
  v.string(),
  v.isoDateTimeSecond('Invalid local timestamp.')
);

v.parse(LocalTimestampSchema, '1995-03-31T00:00:00'); // ✓
v.parse(LocalTimestampSchema, '1995-03-31 00:00:00'); // ✓ (space separator)
v.parse(LocalTimestampSchema, '1995-03-31T00:00:00Z'); // ✗ (timezone not allowed)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Allow ISO 8601 timestamps with local time in isoTimestamp action</issue_title>
<issue_description>The isoTimestamp action only allows timestamps with a timezone designator such as UTC or a time offset. However, local timestamps without timezone should also be considered valid.

https://en.wikipedia.org/wiki/ISO_8601#Local_time_(unqualified)

Example: 1995-03-31T00:00:00

I'm working with an external data source that is scoped to a specific country with a uniform timezone and does only contain timestamps without timezone information.
</issue_description>

<agent_instructions>Read the issue comments and follow the implementation plan</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@fabian-hiller @marianheinsen sorry for the late reply. Is this this relevant? If so, I will look into it. @fabian-hiller @dosu do a deep research and tell me what you think about this issue @fabian-hiller Hey I think I would expand the `isoDateTime` regex to support it or introduce a new `isoDateTimeSecond` action. This would fit into our current naming implementation. Happy to receive feedback on that. In the meantime I recommend using `regex` as a workaround. @fabian-hiller Here is a plan for the implementation:

Plan: Add isoDateTimeSecond Action

Context

GitHub issue #1355: isoTimestamp requires a timezone designator, and isoDateTime only accepts hh:mm (no seconds). There's no action for local date-time with seconds like 1995-03-31T00:00:00. A new isoDateTimeSecond action fills this gap, consistent with the existing isoTime/isoTimeSecond naming pattern.

Regex

ISO_DATE_TIME_SECOND_REGEX = /^\d{4}-(?:0[1-9]|1[0-2])-(?:[12]\d|0[1-9]|3[01])[T ](?:0\d|1\d|2[0-3])(?::[0-5]\d){2}$/u

Format: yyyy-mm-ddThh:mm:ss — no fractional seconds (consistent with isoTimeSecond which also has no fractions).

Files to Create

1. library/src/actions/isoDateTimeSecond/isoDateTimeSecond.ts

Modeled after isoDateTime.ts:

• IsoDateTimeSecondIssue interface — type: 'iso_date_time_second'
• IsoDateTimeSecondAction interface — type: 'iso_date_time_second', reference: typeof isoDateTimeSecond
• Two overloads (no message / with message) + implementation
• JSDoc format: yyyy-mm-ddThh:mm:ss
• _addIssue(this, 'date-time-second', dataset, config)
• Import ISO_DATE_TIME_SECOND_REGEX from ../../regex.ts

2. library/src/actions/isoDateTimeSecond/isoDateTimeSecond.test.ts

Modeled after isoDateTime.test.ts:

• Action object structure tests (undefined/string/function message)
• Untyped input passthrough test
• Valid inputs: '0000-01-01T00:00:00', '9999-12-31T23:59:59', '2023-07-11T19:34:56'
• Valid with space separator: '0000-01-01 00:00:00', '2023-07-11 17:26:30', '9999-12-31 23:59:59'
• Invalid: empty strings, blank spaces, missing separators, wrong separators, invalid year/month/day/hour/minute/second

3. library/src/actions/isoDateTimeSecond/isoDateTimeSecond.test-d.ts

Modeled after isoDateTime.test-d.ts:

• Type tests for action object with undefined/string/function message
• InferInput, InferOutput, InferIssue type inference tests

4. library/src/actions/isoDateTimeSecond/index.ts

export * from './isoDateTimeSecond.ts';

Files to Modify

5. library/src/regex.ts (line ~103)

Add after ISO_DATE_TIME_REGEX:

/**
 * [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) date-time with seconds regex.
 */
export const ISO_DATE_TIME_SECOND_REGEX: RegExp =
  /^\d{4}-(?:0[1-9]|1[0-2])-(?:[12]\d|0[1-9]|3[01])[T ](?:0\d|1\d|2[0-3])(?::[0-5]\d){2}$/u;

6. library/src/actions/index.ts (line ~43)

Add after the isoDateTime export:

export * from './isoDateTimeSecond/index.ts';

Website Documentation

All new files are modeled after the existing isoDateTime docs. Use the repo-website-api-create skill for detailed conventions.

7. website/src/routes/api/(actions)/isoDateTimeSecond/properties.ts

Modeled after isoDateTime/properties.ts. Defines TInput, TMessage, message, and Action properties with types referencing IsoDateTimeSecondIssue and IsoDateTimeSecondAction.

import type { PropertyProps } from '~/components';

export const properties: Record<string, PropertyProps> = {
  TInput: {
    modifier: 'extends',
    type: 'string',
  },
  TMessage: {
    modifier: 'extends',
    type: {
      type: 'union',
      options: [
        {
          type: 'custom',
          name: 'ErrorMessage',
          href: '../ErrorMessage/',
          generics:...

</details>



<!-- START COPILOT CODING AGENT SUFFIX -->

- Fixes open-circle/valibot#1355

<!-- START COPILOT CODING AGENT TIPS -->
---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our [2 minute survey](https://gh.io/copilot-coding-agent-survey).

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
valibot	Ready	Preview, Comment	Mar 8, 2026 10:57pm

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/valibot@1418

commit: 7d3fc90

[Copilot]

Pull request overview

Adds a new isoDateTimeSecond validation action to cover ISO 8601 local date-times with seconds (no timezone designator), complementing existing isoDateTime (minutes) and isoTimestamp (timezone required).

Changes:

• Introduces ISO_DATE_TIME_SECOND_REGEX (yyyy-mm-ddThh:mm:ss, also allowing a space separator).
• Adds isoDateTimeSecond action (+ types) with runtime + type-level tests and exports it from the actions barrel.
• Documents the new action/types and links them from the API menu and pipelines guide.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
website/src/routes/guides/(main-concepts)/pipelines/index.mdx	Adds isoDateTimeSecond to the validation actions list.
website/src/routes/api/menu.md	Adds API menu entries for isoDateTimeSecond and its action/issue types.
website/src/routes/api/(types)/IsoDateTimeSecondIssue/properties.ts	Defines property metadata for IsoDateTimeSecondIssue docs.
website/src/routes/api/(types)/IsoDateTimeSecondIssue/index.mdx	Adds the API docs page for IsoDateTimeSecondIssue.
website/src/routes/api/(types)/IsoDateTimeSecondAction/properties.ts	Defines property metadata for IsoDateTimeSecondAction docs.
website/src/routes/api/(types)/IsoDateTimeSecondAction/index.mdx	Adds the API docs page for IsoDateTimeSecondAction.
website/src/routes/api/(actions)/isoDateTimeSecond/properties.ts	Defines property metadata for isoDateTimeSecond docs.
website/src/routes/api/(actions)/isoDateTimeSecond/index.mdx	Adds the API docs page for isoDateTimeSecond.
library/src/regex.ts	Adds ISO_DATE_TIME_SECOND_REGEX.
library/src/actions/isoDateTimeSecond/isoDateTimeSecond.ts	Implements the new validation action and related interfaces.
library/src/actions/isoDateTimeSecond/isoDateTimeSecond.test.ts	Adds runtime tests for action shape and validation behavior.
library/src/actions/isoDateTimeSecond/isoDateTimeSecond.test-d.ts	Adds type-level tests for overloads and inferred types.
library/src/actions/isoDateTimeSecond/index.ts	Exports isoDateTimeSecond from its folder barrel.
library/src/actions/index.ts	Exports the new action folder from the actions barrel.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[Copilot]

The new action is intended to validate local date-times (no timezone designator), but the test suite doesn’t currently include an explicit case like 1995-03-31T00:00:00Z / ...+01:00 to assert that timezone suffixes are rejected. Adding a couple of these to the invalid inputs list would prevent accidental regex broadening in the future.

Suggested change

	test('for timezone designators', () => {
	expectActionIssue(action, baseIssue, [
	'1995-03-31T00:00:00Z',
	'1995-03-31T00:00:00+01:00',
	]);
	});