Time without surprises

now() does not exist

Calling now() or timestamp() is error E0533. This is not an omission but a design decision (D13): the current time would make a config irreproducible, breaking --dry-run comparisons, caching, and the whole idea that two runs give the same result.

If you genuinely need the build time, the host passes it in:

built_at: env("BUILD_TIME", "unknown")

BUILD_TIME=$(date -u +%FT%TZ) aura eval app.aura --allow-env=BUILD_TIME

The decision about time is made and recorded by whoever runs the tool, and the config stays a pure function of its inputs.

Durations

Timeouts and TTLs are strings with d / h / m / s units, parsed into seconds as an Int:

ttl = "1h30m".parse_duration() # → 5400
cache:
  ttl_seconds:   ttl
  refresh_every: (ttl / 3).format_duration() # → "30m"
end

From there it is ordinary integer arithmetic: adding, subtracting, converting a day into hours. A malformed string is E0319.

Dates

RFC 3339 ↔ epoch seconds, in UTC:

start = "2026-07-18T22:00:00Z".parse_datetime()      # → an epoch Int
window:
  start: start
  end: (start + "4h".parse_duration()).format_datetime()
  # → "2026-07-19T02:00:00Z" — crossing midnight works correctly
end

Offsets are supported (+02:00 denotes the same instant), as is the short date form ("2026-07-18" is midnight UTC). A malformed date is E0320.

Higher-level calendar arithmetic — “plus three months”, working days, time zones — is deliberately outside the core. That is territory for community packages built on top of these epoch primitives.