Standardize date/time handling on ISO8601

[gdevenyi]

Summary

Standardize all date/time handling on ISO8601 across the codebase. Adds Luxon as the date library, introduces shared helpers in @databank/core, and fixes every non-compliant emission/display site found in a full audit.

Audit findings (now fixed)

• API emitted non-ISO strings — toDateString() ("Wed Jul 14 2026") in dataset row payloads and CSV metadata exports.
• 14× toLocaleDateString() with no locale arg in web/ — locale-indeterminate display.
• Prisma @db.Date on createdAt/updatedAt truncated the time portion.
• Loose client parsing — z.coerce.date() accepted non-ISO strings.
• Divergent User type declared dates as number (unix ms).
• Magic constants (24 * 3600 * 1000) in polars day-since-epoch conversion.

Changes by commit

1. add luxon and ISO8601 date helpers in core — new core/src/dates.ts exporting formatISODate, formatISODateTime, parseISODate (all UTC-forced).
2. emit ISO8601 datetimes in dataset rows and CSV metadata — toDateString() → formatISODateTime() in tabular-data.service.ts and datasets.service.ts.
3. render ISO8601 dates in web UI via core helper — 14 toLocaleDateString() sites → formatISODate() (ISO date-only display).
4. migrate Prisma createdAt/updatedAt to full DateTime — drop @db.Date from User, Dataset, Project, SetupConfig.
5. align User type and project query parsing with ISO8601 — User date fields number → Date | null | undefined; z.coerce.date() → z.union([z.iso.datetime(), z.iso.date()]).transform(parseISODate).
6. replace date magic constants and simplify new Date calls — MS_PER_DAY named constant with explanatory comment; new Date(Date.now()) → new Date().

Notes

• i18n: UI now renders ISO date-only (2026-07-14) uniformly across en/fr locales. This is an intentional decision from the audit — flag if localized display is preferred instead.
• Deploy: requires prisma db push (or app sync) so MongoDB reflects the dropped @db.Date. Existing docs keep their midnight-UTC instants, so reads stay consistent.
• Out of scope: polars tryParseDates: true upload-date format validation (file-upload.processor.ts) — deferred to a separate task.

Verification

• pnpm lint — clean across core, api, web
• pnpm test — 17/17 passing

[Copilot]

Pull request overview

This PR standardizes date/time handling across the monorepo by introducing shared ISO8601 helpers in @databank/core, updating API emissions/exports to use ISO8601 datetimes, and replacing locale-dependent UI rendering with deterministic ISO date-only display.

Changes:

• Added Luxon-backed formatISODate, formatISODateTime, and parseISODate helpers in @databank/core and exported them for cross-package use.
• Updated web/ routes and useProjectQuery to render/parse dates using the shared ISO helpers instead of toLocaleDateString() and z.coerce.date().
• Updated API services to emit ISO8601 datetimes and adjusted Prisma schemas to store full DateTime (removing @db.Date truncation), plus a small Date construction cleanup and a named MS_PER_DAY constant.

Reviewed changes

Copilot reviewed 21 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
web/src/routes/portal/projects/index.tsx	Replace locale-dependent expiry display with formatISODate.
web/src/routes/portal/projects/$projectId/index.tsx	Standardize project/dataset created/updated/expiry display to ISO date-only.
web/src/routes/portal/projects/$projectId/datasets.$datasetId/index.tsx	Standardize dataset created/updated display to ISO date-only.
web/src/routes/portal/projects/$projectId/add-dataset.tsx	Standardize dataset created display to ISO date-only.
web/src/routes/portal/datasets/index.tsx	Standardize dataset created display to ISO date-only.
web/src/routes/portal/datasets/$datasetId/index.tsx	Standardize dataset created/updated display to ISO date-only.
web/src/routes/_public/datasets/index.tsx	Standardize public dataset created display to ISO date-only.
web/src/routes/_public/datasets/$datasetId.tsx	Standardize public dataset created/updated display to ISO date-only.
web/src/hooks/queries/useProjectQuery.ts	Tighten project date parsing to ISO-only inputs via parseISODate.
pnpm-workspace.yaml	Add Luxon and Luxon types to the workspace catalog.
pnpm-lock.yaml	Lockfile updates for Luxon and @types/luxon.
core/src/users.ts	Align User date fields’ TypeScript types with Date semantics.
core/src/index.ts	Re-export new dates helpers from the core package entrypoint.
core/src/dates.ts	New shared ISO8601 formatting/parsing helpers backed by Luxon.
core/package.json	Add Luxon dependency and @types/luxon devDependency.
api/src/tabular-data/tabular-data.service.ts	Emit ISO8601 datetimes for dataset-row DATETIME values.
api/src/datasets/datasets.service.ts	Emit ISO8601 datetimes in exported CSV metadata (datetime min/max).
api/src/columns/columns.service.ts	Replace magic milliseconds-per-day constant with MS_PER_DAY.
api/src/auth/auth.service.ts	Simplify new Date(Date.now()) to new Date().
api/prisma/schema/setup.prisma	Store full DateTime (remove @db.Date) for setup timestamps.
api/prisma/schema/projects.prisma	Store full DateTime (remove @db.Date) for project timestamps.
api/prisma/schema/_main.prisma	Store full DateTime (remove @db.Date) for user/dataset timestamps.

Files not reviewed (1)

• pnpm-lock.yaml: Generated file

---

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

[gdevenyi]

Valid point. Fixed in 8047fde: now validates DateTime.isValid and throws TypeError before formatting, mirroring the existing parseISODate pattern. The non-null assertion is now unreachable on the invalid path.

[gdevenyi]

Valid point. Fixed in 8047fde: now validates DateTime.isValid and throws TypeError before formatting, mirroring the existing parseISODate pattern. The non-null assertion is now unreachable on the invalid path.