diff --git a/frontend/src/utils/__tests__/resolutionDate.property.test.js b/frontend/src/utils/__tests__/resolutionDate.property.test.js
index aa38c65..bb859a2 100644
--- a/frontend/src/utils/__tests__/resolutionDate.property.test.js
+++ b/frontend/src/utils/__tests__/resolutionDate.property.test.js
@@ -43,6 +43,14 @@ function isValidCalendarYmd(s) {
   return true;
 }
 
+// True iff `s` is an ISO datetime string whose date prefix is a valid calendar date.
+// e.g. "2026-07-01T00:00:00.000Z" → true (the helper now extracts the date prefix).
+function isIsoDateTimeWithValidDate(s) {
+  if (typeof s !== 'string') return false;
+  if (!/^\d{4}-\d{2}-\d{2}T/.test(s)) return false;
+  return isValidCalendarYmd(s.slice(0, 10));
+}
+
 // --- Shared arbitraries -----------------------------------------------------
 
 // Four-digit zero-padded year string (0000–9999) — always matches \d{4}.
@@ -130,7 +138,7 @@ const wrongShapeArb = fc.oneof(
 
 const invalidStringArb = fc
   .oneof(wrongShapeArb, badMonthArb, badDayArb, impossibleDayArb, twoDigitArb)
-  .filter(s => typeof s === 'string' && s.trim() !== '' && !isValidCalendarYmd(s.trim()));
+  .filter(s => typeof s === 'string' && s.trim() !== '' && !isValidCalendarYmd(s.trim()) && !isIsoDateTimeWithValidDate(s.trim()));
 
 // Any input category (used for totality / independence properties).
 const anyInputArb = fc.oneof(
diff --git a/frontend/src/utils/__tests__/resolutionDate.test.js b/frontend/src/utils/__tests__/resolutionDate.test.js
index 0cb346d..aa40d23 100644
--- a/frontend/src/utils/__tests__/resolutionDate.test.js
+++ b/frontend/src/utils/__tests__/resolutionDate.test.js
@@ -32,6 +32,13 @@ describe('formatResolutionDate', () => {
         value: '2024-02-29',
       });
     });
+
+    it("classifies an ISO datetime '2026-07-03T00:00:00.000Z' as set with the date prefix", () => {
+      expect(formatResolutionDate('2026-07-03T00:00:00.000Z')).toEqual({
+        state: 'set',
+        value: '2026-07-03',
+      });
+    });
   });
 
   describe('invalid — present but not a valid calendar date (Requirement 1.6)', () => {
diff --git a/frontend/src/utils/resolutionDate.js b/frontend/src/utils/resolutionDate.js
index 64178c8..34845ba 100644
--- a/frontend/src/utils/resolutionDate.js
+++ b/frontend/src/utils/resolutionDate.js
@@ -63,14 +63,20 @@ export function formatResolutionDate(raw) {
   }
 
   // Must match the strict YYYY-MM-DD shape.
-  if (!YMD_SHAPE.test(trimmed)) {
+  // Also accept ISO datetime strings (e.g. "2026-07-03T00:00:00.000Z") by
+  // extracting the date prefix — the pg driver returns DATE columns this way.
+  let candidate = trimmed;
+  if (!YMD_SHAPE.test(candidate) && /^\d{4}-\d{2}-\d{2}T/.test(candidate)) {
+    candidate = candidate.slice(0, 10);
+  }
+  if (!YMD_SHAPE.test(candidate)) {
     return { state: 'invalid' };
   }
 
   // Shape is correct; verify it is a real calendar date.
-  const year = Number(trimmed.slice(0, 4));
-  const month = Number(trimmed.slice(5, 7));
-  const day = Number(trimmed.slice(8, 10));
+  const year = Number(candidate.slice(0, 4));
+  const month = Number(candidate.slice(5, 7));
+  const day = Number(candidate.slice(8, 10));
 
   if (month < 1 || month > 12) {
     return { state: 'invalid' };
@@ -80,7 +86,7 @@ export function formatResolutionDate(raw) {
     return { state: 'invalid' };
   }
 
-  // Valid calendar date; the trimmed value is already the canonical
+  // Valid calendar date; the candidate value is the canonical
   // zero-padded YYYY-MM-DD form.
-  return { state: 'set', value: trimmed };
+  return { state: 'set', value: candidate };
 }