diff --git a/src/data/firmsAdapt.js b/src/data/firmsAdapt.js
index 312838e80..18d9fc110 100644
--- a/src/data/firmsAdapt.js
+++ b/src/data/firmsAdapt.js
@@ -81,21 +81,44 @@ export function parseAcquisitionMs(date, time, cache = new Map()) {
   const cached = cache.get(key);
   if (cached !== undefined) return cached;
 
+  // Same calendar as the CSV gate. Date.UTC would otherwise roll 30 February
+  // into March, and the fire's age would describe a detection that never happened.
+  if (!/^\d{4}-\d{2}-\d{2}$/.test(date)) {
+    cache.set(key, 0);
+    return 0;
+  }
+  const timeText = String(time ?? '').trim();
+  if (!/^\d{1,4}$/.test(timeText)) {
+    cache.set(key, 0);
+    return 0;
+  }
+  const hhmm = timeText.padStart(4, '0');
   const year = Number(date.slice(0, 4));
   const month = Number(date.slice(5, 7));
   const day = Number(date.slice(8, 10));
-  const hhmm = String(time ?? '0000').padStart(4, '0');
   const hours = Number(hhmm.slice(0, 2));
   const minutes = Number(hhmm.slice(2, 4));
-  const valid =
-    Number.isFinite(year) &&
-    Number.isFinite(month) &&
-    Number.isFinite(day) &&
-    Number.isFinite(hours) &&
-    Number.isFinite(minutes);
-  const ms = valid ? Date.UTC(year, month - 1, day, hours, minutes) : 0;
-  cache.set(key, ms);
-  return ms;
+  if (
+    month < 1 ||
+    month > 12 ||
+    day < 1 ||
+    day > 31 ||
+    hours > 23 ||
+    minutes > 59
+  ) {
+    cache.set(key, 0);
+    return 0;
+  }
+  const ms = Date.UTC(year, month - 1, day, hours, minutes);
+  const parsed = new Date(ms);
+  const result =
+    parsed.getUTCFullYear() === year &&
+    parsed.getUTCMonth() === month - 1 &&
+    parsed.getUTCDate() === day
+      ? ms
+      : 0;
+  cache.set(key, result);
+  return result;
 }
 
 /**
diff --git a/src/data/firmsAdapt.test.mjs b/src/data/firmsAdapt.test.mjs
index 0e1e56dd6..fa5de9e69 100644
--- a/src/data/firmsAdapt.test.mjs
+++ b/src/data/firmsAdapt.test.mjs
@@ -63,12 +63,39 @@ test('unpadded acq_time parses in the adapter path ("45" = 00:45Z)', () => {
 
 test('parseAcquisitionMs: memo cache is honored, invalid input → 0', () => {
   const cache = new Map();
-  assert.equal(parseAcquisitionMs('2026-07-16', '1006', cache), Date.UTC(2026, 6, 16, 10, 6));
+  assert.equal(
+    parseAcquisitionMs('2026-07-16', '1006', cache),
+    Date.UTC(2026, 6, 16, 10, 6),
+  );
   assert.equal(cache.size, 1);
-  assert.equal(parseAcquisitionMs('2026-07-16', '1006', cache), Date.UTC(2026, 6, 16, 10, 6));
+  assert.equal(
+    parseAcquisitionMs('2026-07-16', '1006', cache),
+    Date.UTC(2026, 6, 16, 10, 6),
+  );
   assert.equal(parseAcquisitionMs(undefined, '1006', cache), 0);
 });
 
+test('impossible acquisition dates stay untimed instead of rolling forward', () => {
+  for (const [date, time] of [
+    ['2026-02-30', '1200'],
+    ['2026-04-31', '1200'],
+    ['2026-13-01', '1200'],
+    ['2026-07-16', '2400'],
+    ['2026-07-16', '1260'],
+  ]) {
+    assert.equal(parseAcquisitionMs(date, time), 0, `${date}:${time}`);
+    const [fire] = adaptFirmsRecords([
+      proxyRecord({ acqDate: date, acqTime: time }),
+    ]);
+    assert.equal(fire.acqMs, 0, `${date}:${time}`);
+    assert.equal(fire.lat, 38.99488);
+  }
+  const [leap] = adaptFirmsRecords([
+    proxyRecord({ acqDate: '2024-02-29', acqTime: '45' }),
+  ]);
+  assert.equal(leap.acqMs, Date.UTC(2024, 1, 29, 0, 45));
+});
+
 test('daynight "D" → night false', () => {
   const [fire] = adaptFirmsRecords([proxyRecord({ daynight: 'D' })]);
   assert.equal(fire.night, false);
@@ -89,11 +116,16 @@ test('records with non-finite lat/lon are skipped; index stays sequential', () =
     proxyRecord({ lat: 40.1 }),
   ]);
   assert.equal(fires.length, 2);
-  assert.deepEqual(fires.map((f) => f.index), [0, 1]);
+  assert.deepEqual(
+    fires.map((f) => f.index),
+    [0, 1],
+  );
 });
 
 test('non-finite frp/brightness → 0; empty input → []', () => {
-  const [fire] = adaptFirmsRecords([proxyRecord({ frp: 'n/a', brightness: undefined })]);
+  const [fire] = adaptFirmsRecords([
+    proxyRecord({ frp: 'n/a', brightness: undefined }),
+  ]);
   assert.equal(fire.frp, 0);
   assert.equal(fire.brightness, 0);
   assert.deepEqual(adaptFirmsRecords([]), []);