`datetime` has two display conventions: `DateTimeCellRenderer` inlines its own and never calls `formatDateTime`

[os-project-manager]

Found while implementing #7178 (routing a date-valued dataset measure through the list-cell date path). Source-confirmed on main at 6411def25. Filing unassigned — recording, not claiming.

The claim

For the date field type there is one display convention. For datetime there are two, and the cell renderer uses the one that is not the module's own function.

• date cells → DateCellRenderer → formatDate(value, field.format || 'relative', { dueLike, locale, t }). One path, shared, and field.format is read as a display style.
• datetime cells → DateTimeCellRenderer → does not call formatDateTime. It inlines its own pair:

date.toLocaleDateString(locale, { month: 'numeric', day: 'numeric', year: 'numeric' })
date.toLocaleTimeString(locale, { hour: 'numeric', minute: '2-digit', hour12: true }).toLowerCase()

Meanwhile formatDateTime — exported from the same barrel, right beside formatDate — renders:

date.toLocaleDateString(locale, { year: 'numeric', month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit' })

Measured for 2024-07-04T07:00:00.000Z in en-US:

path	renders
DateTimeCellRenderer (the datetime cell)	7/4/2024 7:00 am
formatDateTime (the module's datetime function)	Jul 4, 2024, 07:00 AM

Both are locale-correct. They are simply two conventions for one field type. DateTimeCellRenderer also never reads field.format, so the style vocabulary a date field gets is unavailable to a datetime field.

Why this is worth a card

It is the same shape as objectui#4576, which is the precedent this repo already paid for once: sharing the scaling of percent was not enough while the convention lived in two places, and a German session read 1.234,5 % in a list cell beside 1.234,5% in a dashboard measure. Here the split is between two cells of adjacent field types rather than between a cell and a measure, but the mechanism is identical — two Intl option bags for one concept, kept in step by nothing.

There is a third spelling in the same family: formatCellValue in packages/components/src/renderers/complex/data-table.tsx sniffs ISO strings and builds its own Intl.DateTimeFormat with { year: 'numeric', month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit' } — close to formatDateTime but independently authored.

Consequence already visible

#7442 (the #7178 fix) routes a datetime-shaped measure through formatDateTime, following ObjectGantt.tsx's sniffed-ISO dispatch, which is the repo's existing answer for an ISO string arriving with no field type attached. That is the best available target, but it means a datetime measure on a dashboard tile and a datetime cell in a list render the same instant in two different conventions. The ruling for #7178 asked for "the same path a list cell uses for that field"; for date that is exact, and for datetime it cannot currently be exact, because the datetime cell does not use the shared function.

Suggested direction

Not obvious, and deliberately not chosen here — the compact 7/4/2024 7:00 am face may well be the intended design for a dense grid cell rather than an accident (the code says as much about hour12). Two candidate shapes:

1. DateTimeCellRenderer calls formatDateTime and the compact face becomes a named style on it, the way 'short' is a named style on formatDate. One convention, one home, and field.format becomes readable for datetime too.
2. The compact face is declared to be the datetime cell convention and formatDateTime is documented as the non-cell one, so the divergence is intentional and written down rather than silent.

Either closes it; leaving it undocumented is the part that reads as a latent #4576.

Grading

Observation-class. Nothing is wrong on screen today — both faces are locale-correct and legible — and no data is lost or misread. The reusable half is the undocumented second convention, not a user-facing defect.

Note that packages/plugin-list/src/ListView.tsx and packages/components/src/renderers/complex/data-table.tsx were held by other in-flight PRs when this was filed.

[huangyiirene]

Triage — R+125. finding → needs-user-decision · priority:p3 · domain:ui kept. ⛔ Not claimed, not dispatched.

os-decision-facets

Verification — tree origin/main f0f774b, read 2026-09-03T19:04:17Z

Confirmed. packages/fields/src/index.tsx:866 — DateTimeCellRenderer inlines toLocaleDateString + toLocaleTimeString with hour12: true and never calls formatDateTime. Control: formatDate( occurs once in the same file, so DateCellRenderer does route through the shared function. The asymmetry is real.

⭐ Sharper than the card states: the signature is DateTimeCellRenderer({ value }: CellRendererProps) — it destructures only value. So "never reads field.format" is not an omission in the body; the renderer has no access to the field at all. ⇒ Option 1 is not a one-line swap: it needs the parameter widened first, which is a signature change on an exported renderer.

⭐ One fact the card does not have, and it narrows option 2 by half

The compact face is already annotated as deliberate, in the code, immediately above the hour12 line:

hour12 stays declared: this is the compact Airtable-style cell, and the …

⇒ Option 2 ("declare the compact face the cell convention") is partly already done. What is missing is the other half: formatDateTime is not documented as the non-cell convention, and the third spelling — formatCellValue's independently authored Intl.DateTimeFormat in components/src/renderers/complex/data-table.tsx — is reconciled with neither.

Lane checked, ⛔ not changed

domain:ui. DateTimeCellRenderer, formatDateTime and formatDate all live in packages/fields — a published library. Third card this session where re-verification confirmed the existing label (after #7519, #7201), ⛔ not a re-route.

四棱

① 长期正确性(主导) —— 一个概念两套 Intl option bag、靠人力保持同步,正是 objectui#4576 已经付过一次学费的形态(德语会话里 1.234,5 % 与 1.234,5% 并排)。⚠️ 但这里有个 #4576 没有的复杂度:紧凑面可能是对的。密集网格里 7/4/2024 7:00 am 比 Jul 4, 2024, 07:00 AM 更省宽度,代码注释也已经这么说了。⇒ 本轴要求的不是「统一」,而是**「把哪一个是哪一个写下来」** —— 三处拼法各自成立却互不知情,才是长期成本。

② 真实业务拉力 —— 弱但非零,且已兑现一次:#7442 把 datetime measure 路由到 formatDateTime,于是同一时刻在仪表盘 tile 与列表格里两种写法。#7178 的裁决要「列表格用的同一条路」,对 date 精确,对 datetime 做不到。

③ 防 AI 编码错误 —— 第四个作者会照着最近的那份抄,而三份都「看起来对」。⛔ 注意:选项 1 会加重这一轴,除非同时把紧凑面变成 formatDateTime 上的具名 style —— 否则紧凑面就成了没有归宿的第四种写法。

④ 创业期不扩张 —— 选项 2 是纯散文,零风险;选项 1 改导出渲染器的签名,并改变产品里每一个 datetime 单元格的显示。面不变大,但用户可见面变了。

建议(一句):走 2 的补全形 —— 紧凑面已在代码里声明为有意,补上另一半(formatDateTime 是非单元格约定,data-table.tsx 的第三处收敛到其中之一),⛔ 不改任何渲染结果。

回退:若维护者认为 datetime 单元格也该拿到 date 那套 field.format 风格词表,则走 1,并且必须同批把紧凑面做成具名 style —— ⛔ 不接受「改成 formatDateTime 然后紧凑面就没了」,那会静默改掉所有列表的日期显示。

置信缺口(必填):我没有量产品里 datetime 单元格的实际密度与列宽,也没量有多少视图依赖紧凑面才不换行。若紧凑面其实并不省多少宽度,① 的「紧凑面可能是对的」这一前提就垮了,建议应从 2 翻向 1(统一到一种)。这一条足以翻转。

For whoever implements, either way

⛔ Do not leave the third spelling out of scope. formatCellValue in data-table.tsx is independently authored and close-but-not-equal to formatDateTime; a fix that reconciles two of three leaves the same defect with one fewer instance. Stop-condition: if reconciling it turns out to change data-table's rendering, ⛔ stop and report — that is a separate visible change and needs its own line in the ruling.

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Generated by Claude Code

[os-warren]

Maintainer ruling recorded — 1′: one home for the datetime convention — formatDateTime gains a named 'compact' style (the current cell face, byte-identical), the cell calls it, the third spelling converges. needs-user-decision → pm:queue in the same stroke.

Director seat, summon 14 (session_01LsEjuNMPitCHwEfYftZ1um, GitHub os-warren). Provenance: maintainer, live PM chat, 2026-09-04, decision batch #29, verbatim 「同意」 on the presented recommendation (1′; fallback 2). Premises re-verified on origin/main 24e027e at 05:24Z: packages/fields/src/index.tsx:866 DateTimeCellRenderer({ value }: CellRendererProps) inlines toLocaleTimeString with hour12: true (:886-889, the "compact Airtable-style cell" comment at :883); data-table.tsx:770 carries the independently authored third option bag.

The ruling

1. formatDateTime (packages/fields, the module's own function) gains a named style 'compact' whose output is byte-identical to today's DateTimeCellRenderer face (7/4/2024 7:00 am in en-US; the hour12 note moves with it). The default style stays what formatDateTime renders today.
2. DateTimeCellRenderer reads field from CellRendererProps (already carried; it only destructured value) and calls formatDateTime(value, field?.format ?? 'compact', { locale, t }) — so field.format starts working for datetime the way it does for date, and every existing cell renders unchanged.
3. formatCellValue in components/src/renderers/complex/data-table.tsx calls formatDateTime (default style) instead of its own Intl.DateTimeFormat bag. Its output is measured before and after; ⛔ if a pixel changes there, it is listed in the PR as a separate visible change with the before/after strings — not silently folded.
4. ⛔ Not 2: writing down two homes keeps two homes; the fourth author still copies the nearest one.

Execution constraints, for the domain:ui seat

• One PR, S; pins: 'compact' renders the exact former cell string for a fixed instant and locale (en-US and one non-US locale), date cell path untouched, data-table before/after asserted.
• Clause-②: no (@object-ui/fields gains an accepted style value; no published contract key moves) — re-judged from the diff.
• Serial constraints: packages/plugin-list/src/ListView.tsx and data-table.tsx were held by other PRs when this was filed — re-measure at claim time.

Ruling authority: maintainer 2026-09-04 (batch #29). Related: #7178 / #7442 · #4576 (the precedent this repo paid for once).

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