Root-cause fix for tonight's repeated red `main`, instead of repointing
stamps one at a time — **four PRs across three lanes did that in ninety
minutes** (#3261, #3269, and my #3263 and #3272, two of which I closed
as superseded by concurrent work).
## The defect
The fleet writes stamps from **many** machines; this gate evaluates them
on **one**.
#2941 fixed the case where the author sits **west** of the runner — a
correct 5pm-in-California stamp read as "tomorrow" under a UTC
comparison — by switching to the runner's **local** calendar. The mirror
case was left open, and that is what broke `main`:
| commit | landed (PDT) | = UTC | stamp written |
|---|---|---|---|
| `9094d1640e` | 16:12 | 23:12 Jul 31 | `2026-08-01-00:20` |
| `e52da740a5` | 16:32 | 23:32 Jul 31 | `2026-08-01-00:50` |
| `3f95c6d53e` | 16:40 | 23:40 Jul 31 | `2026-08-01-01:05` |
Those are **neither** the runner's local date **nor** UTC. They are the
*author's* local date in a UTC+1 container — and they are **correct** by
this project's own convention ("authors write the local date"). The
gate, running in PDT, called all three "tomorrow" and reddened `main`
for every other lane.
## The fix
A stamp is future only if it is ahead of **both** the local and UTC
calendar dates.
- Accepts both honest directions (author east or west of the runner).
- **Preserves #2941**, doesn't revert it — west of Greenwich the local
date is the earlier of the pair, so the 5pm-in-California case still
passes.
- Still catches an invented date: `scheduler.ts`'s `2026-08-06` stamp
(six days out) remains counted, and a mutation probe at `2026-09-15`
fails the gate.
## AGENTS.md corrected in the same commit
It still instructed **`date -u`**, which describes the *pre-#2941* gate.
That instruction is now the one that **produces** the failure from any
machine east of the runner — I followed it myself earlier tonight and
repointed stamps that were already correct. Rewritten to say: write your
own local date; the gate accepts anything not ahead of both calendars.
## Baseline
Auto-tightened for **37 files** — the gate's no-author drop path. Those
allowances were false positives carried since the UTC-only era, so this
**strengthens** the ratchet rather than widening it (`scheduler.ts` 2 →
1, keeping the genuinely-invented stamp counted).
## Verification
```
check-fnxc-future-dates green
check-inert-sync-lane-conversions green
check-lane-wiring green
check-sql-column-literals green
census --strict green
MUTATION: FNXC:MutationProbe 2026-09-15-10:00 → gate fails (real future dates still caught)
```
No changeset: tooling/gate + internal docs.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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