fix(blog): compare full ISO timestamps when sorting, and drop posts without a slug

[aka-sacci-ccr]

Two fixes to blog/core/handlePosts.ts.

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1. Date sorting ignored full ISO timestamps

The date branch of the sortPosts comparator built a Date by concatenating a time onto whatever was in post.date:

new Date(`${b.date}T00:00:00`).getTime() - new Date(`${a.date}T00:00:00`).getTime()

That assumes every date is exactly YYYY-MM-DD. But BlogPost.date is just a string and the CMS also stores full ISO timestamps. For "2026-08-05T12:51:59Z" the concatenation yields "2026-08-05T12:51:59ZT00:00:00" → Invalid Date → getTime() is NaN → the comparison is NaN.

Per spec (SortCompare: "If v is NaN, return +0") a NaN comparator result is treated as +0, and toSorted is stable — so a post with a full ISO timestamp was never moved. It just stayed wherever the records happened to put it. Symptom: BlogpostList with sortBy: "date_desc" listed yesterday's post above today's.

Timezone dependence, in two rounds

The same expression made ordering depend on the server timezone, because "2026-08-04T00:00:00" carries no timezone designator and is therefore parsed as local midnight.

Fixing that for bare dates alone turned out to be insufficient (review thread): per spec a date-only string is parsed as UTC, but a datetime with no designator is parsed as local. So an offset-less "2026-08-05T23:30:00" still ordered inconsistently against a bare "2026-08-06":

TZ=UTC                  desc: data-pura > sem-offset
TZ=Asia/Tokyo           desc: data-pura > sem-offset
TZ=America/Sao_Paulo    desc: sem-offset > data-pura   <-- flipped
TZ=Pacific/Kiritimati   desc: data-pura > sem-offset

Fix

Any ISO date or datetime lacking a timezone designator is pinned to UTC; strings that already carry a Z or a ±hh:mm offset pass through untouched. The pattern covers minute precision and fractional seconds, not just whole seconds:

const ISO_WITHOUT_TIMEZONE =
  /^\d{4}-\d{2}-\d{2}(T\d{2}:\d{2}(:\d{2}(\.\d+)?)?)?$/;

The || 0 keeps NaN from ever reaching the comparator, so an unparseable date sorts last for desc — consistent with the existing !a[sortMethod] guards, which already push missing values to the end.

Verified against the real sortPosts, including with the input order flipped — since the old behavior depended on the order records arrived in, passing in both directions is what shows it is actually sorting rather than getting lucky:

desc:           [ "2026-08-05T12:51:59Z", "2026-08-04" ]
asc :           [ "2026-08-04", "2026-08-05T12:51:59Z" ]
desc (flipped): [ "2026-08-05T12:51:59Z", "2026-08-04" ]

Every offset-less form resolves to the same instant as its explicit-UTC twin, and the day-boundary ordering above is stable across all five timezones tested.

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2. Posts without a slug were rendered in listings

A post whose slug is missing, empty or blank has no route, so it can never be rendered — but it still appeared in listings, producing cards that link nowhere and a broken url in the JSON-LD.

filterRoutablePosts drops them inside filterPosts, ahead of every other filter and of slicePosts, so count still yields count renderable posts.

The guard checks the type as well as the value, which is load-bearing: records come from getRecordsByPath, which casts the CMS JSON without validating it, so slug is a string only by convention. A non-string slug would make slug.trim() throw inside handlePosts — and the try/catch in BlogpostList turns a throw into logger.error + return null, so one malformed record would blank out the entire listing instead of just dropping itself. Worse than the bug being fixed.

Cases checked against the real handlePosts (only the valid post survives, and an all-invalid input returns null, matching the existing empty-list contract):

slug	result
undefined	dropped
""	dropped
null	dropped
" "	dropped
123	dropped, no throw
all posts invalid	null

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Compatibility

⚠️ Behavior fix, not an API change. The exported signatures of sortPosts and handlePosts are unchanged, and SortBy / VALID_SORT_ORDERS are untouched.

Two visible changes for live sites, both intended:

• Listings will actually re-sort. Posts with full ISO timestamps were previously frozen in records order and will now move to their correct date position. Sites relying on the broken order will see their listings change.
• Posts without a slug disappear from listings. They were never reachable, but they did occupy slots.

Worth a note in the release notes.

Checks

deno task check (the pre-commit hook) passes on every commit: fmt over 2099 files, lint over 1979, and deno check on every mod.ts.

Left out on purpose

• blog/sections/Template.tsx:74 has the same string-concat pattern, but for display — with a full ISO timestamp it renders "Invalid Date". Same root cause, different symptom; kept out to keep this PR scoped.
• No tiebreak for equal dates: migrated posts frequently share a date, and those stay in whatever order the records returned.
• BlogPostPage and BlogPostItem both do posts.find((post) => post.slug === slug). If the route param is ever undefined, that matches a slug-less record; those loaders don't go through handlePosts, so this PR doesn't cover them.
• The localeCompare branch has its inversion backwards for string fields (title_asc returns Z→A). Pre-existing, out of scope, and sites are presumably compensating — but worth a separate issue.

🤖 Generated with Claude Code

[github-actions]

Tagging Options

Should a new tag be published when this PR is merged?

• 👍 for Patch 0.160.1 update
• 🎉 for Minor 0.161.0 update
• 🚀 for Major 1.0.0 update

[coderabbitai]

📝 Walkthrough

Walkthrough

This change updates blog post date parsing in handlePosts. It adds a helper that normalizes bare dates to UTC, uses that helper during sorting, and stores the awaited sorted posts in a local variable before returning them.

Changes

Blog date sorting

Layer / File(s)	Summary
Date normalization and sorting blog/core/handlePosts.ts	Adds dateToTime to parse bare dates as UTC midnight, accept ISO timestamps, and return 0 for invalid values. The date comparison now uses this helper. handlePosts also assigns the awaited sorted posts to sorted before it returns them.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• deco-cx/apps#1572: Both PRs change blog/core/handlePosts.ts date sorting by normalizing bare date strings to UTC before sort comparison.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title partially relates to the changeset. It mentions date sorting with ISO timestamps, which is the first fix, but omits the second fix about dropping posts without a slug.
Description check	✅ Passed	The description comprehensively explains both fixes with technical detail, root causes, and verification results. Required sections from the template are missing (Issue Link, Loom Video, Demonstration Link), but the core contribution is well documented.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-blog-date-sorting

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[cubic-dev-ai]

All reported issues were addressed

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