diff --git a/.jules/bolt.md b/.jules/bolt.md
index b08b203a..a909c4f8 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -4,3 +4,6 @@
 ## 2026-07-12 - Optimize renderTaskRow DOM allocations
 **Learning:** Caching unattached template nodes and instantiating them via `.cloneNode(false)` reduces DOM instantiation overhead in O(N) render loops significantly.
 **Action:** Apply this optimization to other hot-path rendering elements such as rows, cells, and stack containers.
+## 2026-09-03 - Measure date-formatting micro-optimizations before generalizing
+**Learning:** In a bounded Node/V8 microbenchmark, explicit two-digit zero-padding can be faster than `String.prototype.padStart()` for the same formatter output. That measurement does not establish browser Gantt p95, allocation/GC pressure, or a JS/native-boundary root cause.
+**Action:** Preserve formatter behavior with executable UTC/local/zero-padding/invalid-date regression coverage. Apply the inline form only where representative profiling supports it, and keep buyer-visible performance claims separate from microbenchmark evidence.
diff --git a/app.js b/app.js
index a04aae71..0f155ba4 100644
--- a/app.js
+++ b/app.js
@@ -2684,20 +2684,29 @@ function clamp(value, min, max) {
 
 function formatDateInput(date) {
   const year = date.getUTCFullYear();
-  const month = String(date.getUTCMonth() + 1).padStart(2, '0');
-  const day = String(date.getUTCDate()).padStart(2, '0');
+  const monthRaw = date.getUTCMonth() + 1;
+  const dayRaw = date.getUTCDate();
+  const month = monthRaw < 10 ? '0' + monthRaw : monthRaw;
+  const day = dayRaw < 10 ? '0' + dayRaw : dayRaw;
   return `${year}-${month}-${day}`;
 }
 
 function formatLocalDateInput(date) {
   const year = date.getFullYear();
-  const month = String(date.getMonth() + 1).padStart(2, '0');
-  const day = String(date.getDate()).padStart(2, '0');
+  const monthRaw = date.getMonth() + 1;
+  const dayRaw = date.getDate();
+  const month = monthRaw < 10 ? '0' + monthRaw : monthRaw;
+  const day = dayRaw < 10 ? '0' + dayRaw : dayRaw;
   return `${year}-${month}-${day}`;
 }
 
 function formatCompactDate(date) {
-  return `${date.getFullYear()}${String(date.getMonth() + 1).padStart(2, '0')}${String(date.getDate()).padStart(2, '0')}`;
+  const year = date.getFullYear();
+  const monthRaw = date.getMonth() + 1;
+  const dayRaw = date.getDate();
+  const month = monthRaw < 10 ? '0' + monthRaw : monthRaw;
+  const day = dayRaw < 10 ? '0' + dayRaw : dayRaw;
+  return `${year}${month}${day}`;
 }
 
 function formatPercent(value, digits) {
diff --git a/package.json b/package.json
index 8cefdc74..1788011c 100644
--- a/package.json
+++ b/package.json
@@ -13,9 +13,9 @@
     "coverage": "npm run test:coverage",
     "server": "node server/server.mjs",
     "test:api": "node tests/api/auth-secret.test.mjs && node tests/api/smoke.mjs && node tests/api/ratelimit.test.mjs && node tests/api/attachment-status.test.mjs && node tests/api/session-revocation.test.mjs && node tests/api/orchestrator-attribution.test.mjs",
-    "test:unit": "node tests/unit/opencode-config.test.mjs && node tests/unit/changelog-release-notes.test.mjs && node tests/unit/analytics.test.mjs && node tests/unit/cpm.test.mjs && node tests/unit/baseline-compare.test.mjs && node tests/unit/workload.test.mjs && node tests/unit/cost-evm.test.mjs && node tests/unit/msproject.test.mjs && node tests/unit/auth-password.test.mjs && node tests/unit/editor-unsaved.test.mjs && node tests/unit/static-coverage-evidence.test.mjs && node tests/unit/dep-types.test.mjs && node tests/unit/weekly-report.test.mjs && node tests/unit/clearfolio.test.mjs && node tests/unit/clearfolio-adapter-mock-hmac.test.mjs && node tests/unit/orchestrator.test.mjs && node tests/unit/orchestrator-coverage.test.mjs && node tests/unit/orchestrator-attribution.test.mjs && node tests/unit/sprint-stats.test.mjs && node tests/unit/burndown.test.mjs && node tests/unit/pm-analysis.test.mjs && node tests/unit/cloud-sync-security.test.mjs && node tests/unit/attachment-status.test.mjs && node tests/unit/clearfolio-status-signal.test.mjs && node tests/unit/coverage-script-contract.test.mjs && node tests/unit/toast-accessibility.test.mjs",
+    "test:unit": "node tests/unit/opencode-config.test.mjs && node tests/unit/changelog-release-notes.test.mjs && node tests/unit/analytics.test.mjs && node tests/unit/cpm.test.mjs && node tests/unit/baseline-compare.test.mjs && node tests/unit/workload.test.mjs && node tests/unit/cost-evm.test.mjs && node tests/unit/msproject.test.mjs && node tests/unit/auth-password.test.mjs && node tests/unit/editor-unsaved.test.mjs && node tests/unit/static-coverage-evidence.test.mjs && node tests/unit/dep-types.test.mjs && node tests/unit/weekly-report.test.mjs && node tests/unit/clearfolio.test.mjs && node tests/unit/clearfolio-adapter-mock-hmac.test.mjs && node tests/unit/orchestrator.test.mjs && node tests/unit/orchestrator-coverage.test.mjs && node tests/unit/orchestrator-attribution.test.mjs && node tests/unit/sprint-stats.test.mjs && node tests/unit/burndown.test.mjs && node tests/unit/pm-analysis.test.mjs && node tests/unit/cloud-sync-security.test.mjs && node tests/unit/attachment-status.test.mjs && node tests/unit/clearfolio-status-signal.test.mjs && node tests/unit/coverage-script-contract.test.mjs && node tests/unit/toast-accessibility.test.mjs && node tests/unit/date-formatters.test.mjs",
     "test:coverage": "c8 --all --include=app.js --include=cloud-sync.js --include=scripts/ci/static_coverage_evidence.mjs --include=server/attachment_status.mjs --include=server/app.mjs --include=server/auth.mjs --include=server/clearfolio.mjs --include=server/orchestrator.mjs --reporter=json --reporter=json-summary npm run test:coverage:cases",
-    "test:coverage:cases": "node tests/unit/coverage-script-contract.test.mjs && node tests/unit/attachment-status.test.mjs && node tests/unit/clearfolio-status-signal.test.mjs && node tests/unit/clearfolio-adapter-mock-hmac.test.mjs && node tests/unit/orchestrator.test.mjs && node tests/unit/orchestrator-coverage.test.mjs && node tests/unit/orchestrator-attribution.test.mjs && node tests/unit/msproject.test.mjs && node tests/unit/auth-password.test.mjs && node tests/unit/editor-unsaved.test.mjs && node tests/unit/static-coverage-evidence.test.mjs && npm run test:api",
+    "test:coverage:cases": "node tests/unit/coverage-script-contract.test.mjs && node tests/unit/attachment-status.test.mjs && node tests/unit/clearfolio-status-signal.test.mjs && node tests/unit/clearfolio-adapter-mock-hmac.test.mjs && node tests/unit/orchestrator.test.mjs && node tests/unit/orchestrator-coverage.test.mjs && node tests/unit/orchestrator-attribution.test.mjs && node tests/unit/msproject.test.mjs && node tests/unit/auth-password.test.mjs && node tests/unit/editor-unsaved.test.mjs && node tests/unit/static-coverage-evidence.test.mjs && node tests/unit/date-formatters.test.mjs && npm run test:api",
     "test:e2e": "playwright test",
     "test:e2e:headed": "playwright test --headed",
     "test:e2e:cloud": "playwright install chromium && playwright test tests/e2e/cloud.spec.js tests/e2e/toast-accessibility.spec.js",
diff --git a/tests/unit/date-formatters.test.mjs b/tests/unit/date-formatters.test.mjs
new file mode 100644
index 00000000..09fca706
--- /dev/null
+++ b/tests/unit/date-formatters.test.mjs
@@ -0,0 +1,56 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import vm from 'node:vm';
+
+const appPath = resolve('app.js');
+const appSource = readFileSync(appPath, 'utf8');
+
+function loadFunction(name) {
+  const marker = `function ${name}(`;
+  const start = appSource.indexOf(marker);
+  assert.notEqual(start, -1, `${name} must remain defined in app.js`);
+
+  let depth = 0;
+  let opened = false;
+  let end = -1;
+  for (let index = appSource.indexOf('{', start); index < appSource.length; index += 1) {
+    if (appSource[index] === '{') {
+      depth += 1;
+      opened = true;
+    } else if (appSource[index] === '}') {
+      depth -= 1;
+      if (opened && depth === 0) {
+        end = index + 1;
+        break;
+      }
+    }
+  }
+  assert.notEqual(end, -1, `${name} must have a complete function body`);
+
+  const source = appSource.slice(start, end);
+  const lineOffset = appSource.slice(0, start).split('\n').length - 1;
+  return new vm.Script(`(${source})`, {
+    filename: appPath,
+    lineOffset,
+  }).runInThisContext();
+}
+
+const formatDateInput = loadFunction('formatDateInput');
+const formatLocalDateInput = loadFunction('formatLocalDateInput');
+const formatCompactDate = loadFunction('formatCompactDate');
+
+assert.equal(formatDateInput(new Date(Date.UTC(2026, 0, 5))), '2026-01-05');
+assert.equal(formatDateInput(new Date(Date.UTC(2026, 10, 15))), '2026-11-15');
+
+assert.equal(formatLocalDateInput(new Date(2026, 0, 5, 12, 0, 0)), '2026-01-05');
+assert.equal(formatLocalDateInput(new Date(2026, 10, 15, 12, 0, 0)), '2026-11-15');
+assert.equal(formatCompactDate(new Date(2026, 0, 5, 12, 0, 0)), '20260105');
+assert.equal(formatCompactDate(new Date(2026, 10, 15, 12, 0, 0)), '20261115');
+
+const invalid = new Date(Number.NaN);
+assert.equal(formatDateInput(invalid), 'NaN-NaN-NaN');
+assert.equal(formatLocalDateInput(invalid), 'NaN-NaN-NaN');
+assert.equal(formatCompactDate(invalid), 'NaNNaNNaN');
+
+console.log('date formatter tests passed');