catalog / libraries

Date & Time Library

Instants, zoned times, durations and formatting — correct across zones and DST.

18 capabilities 1 sections reference specification

Build against it

# give your agent the catalog — no account, no install
claude mcp add provespec -- npx -y provespec-mcp

# then, from any agent session
spec_get(slug: "date-time")                → the capability tree
spec_checklist(slug: "date-time")          → the questions to answer
spec_grade(slug: "date-time", grades: [...])  → parity % + the gap list

# or just fetch it
curl https://provespec.com/catalog/date-time/spec.json

Grade every capability below as yes · partial · no · na, with a file reference as evidence. Whatever you leave ungraded counts as missing — the gap list is the work queue.

Or just paste this to your agent

Use the ProveSpec MCP server. Fetch the "date-time" spec with
spec_get, then walk spec_checklist and grade this repository against it —
one verdict per capability, each with a file reference as the note.
Call spec_grade with the results and give me the gap list as the plan.

If the server is not registered, add it first:
  claude mcp add provespec -- npx -y provespec-mcp

The specification

AI 18

Types
  • ✓ Instant on the absolute timeline unambiguous, zone-free
  • ✓ Calendar date without a time
  • ✓ Wall time without a date
  • ✓ Zoned date-time instant plus IANA zone
  • ✓ Duration and period are distinct exact time vs calendar amounts
Zones
  • ✓ IANA time zone database support Europe/Berlin
  • ✓ DST transitions handled explicitly skipped and repeated local times resolvable
  • ✓ Convert between zones without losing the instant
Arithmetic
  • ✓ Add and subtract durations
  • ✓ Calendar-aware addition +1 month on Jan 31 documented clamping
  • ✓ Difference between two points in chosen units
  • ✓ Start-of and end-of unit day, week, month
Parsing
  • ✓ ISO 8601 parse and format round-trips exactly
  • ✓ Custom format patterns
  • ✓ Locale-aware human formatting including relative time
Correctness
  • ✓ Values are immutable operations return new values
  • ✓ Leap years and leap seconds documented
  • ✓ Comparison and sorting total order on instants
Open in Parity → Download spec.json All 102 specs