diff --git a/src/duration.ts b/src/duration.ts
index 0195fc2..8e982e9 100644
--- a/src/duration.ts
+++ b/src/duration.ts
@@ -149,17 +149,27 @@ export function elapsedTime(date: Date, precision: Unit = 'second', now = Date.n
   const delta = date.getTime() - now
   if (delta === 0) return new Duration()
   const sign = Math.sign(delta)
-  const ms = Math.abs(delta)
+  // Months below are approximated as 30 days, so a year is 360 days long. Over many years that drift adds up to
+  // whole extra years, so count the whole calendar years first and only approximate what is left over.
+  const earlier = new Date(sign < 0 ? date : now)
+  const later = new Date(sign < 0 ? now : date)
+  let calendarYears = later.getUTCFullYear() - earlier.getUTCFullYear()
+  while (calendarYears > 0 && applyDuration(earlier, new Duration(calendarYears)) > later) calendarYears -= 1
+  const ms =
+    calendarYears > 0
+      ? later.getTime() - applyDuration(earlier, new Duration(calendarYears)).getTime()
+      : Math.abs(delta)
   const sec = Math.floor(ms / 1000)
   const min = Math.floor(sec / 60)
   const hr = Math.floor(min / 60)
   const day = Math.floor(hr / 24)
   const month = Math.floor(day / 30)
-  const year = Math.floor(month / 12)
+  const extraYears = Math.floor(month / 12)
+  const year = Math.max(calendarYears, 0) + extraYears
   const i = unitNames.indexOf(precision)
   return new Duration(
     i >= 0 ? year * sign : 0,
-    i >= 1 ? (month - year * 12) * sign : 0,
+    i >= 1 ? (month - extraYears * 12) * sign : 0,
     0,
     i >= 3 ? (day - month * 30) * sign : 0,
     i >= 4 ? (hr - day * 24) * sign : 0,
diff --git a/test/duration.ts b/test/duration.ts
index 87707de..dd73def 100644
--- a/test/duration.ts
+++ b/test/duration.ts
@@ -225,6 +225,21 @@ suite('duration', function () {
         input: '2023-03-21T16:03:00.000Z',
         expected: '-P1DT20H',
       },
+      {
+        now: '2025-02-06T12:00:00.000Z',
+        input: '2015-02-14T05:13:48.000Z',
+        expected: '-P9Y11M28DT6H46M12S',
+      },
+      {
+        now: '2025-01-01T00:00:00.000Z',
+        input: '2020-01-01T00:00:00.000Z',
+        expected: '-P5Y',
+      },
+      {
+        now: '2025-02-06T00:00:00.000Z',
+        input: '2035-02-14T00:00:00.000Z',
+        expected: 'P10Y8D',
+      },
       {
         now: '2022-10-24T14:46:00.000Z',
         input: '2024-10-24T14:46:00.000Z',
diff --git a/test/relative-time.js b/test/relative-time.js
index 6edb88e..4e422e5 100644
--- a/test/relative-time.js
+++ b/test/relative-time.js
@@ -774,7 +774,7 @@ suite('relative-time', function () {
       time.setAttribute('tense', 'past')
       time.setAttribute('datetime', '2023-01-01T00:00:00Z')
       await Promise.resolve()
-      assert.equal(time.shadowRoot.textContent, '11 years ago')
+      assert.equal(time.shadowRoot.textContent, '10 years ago')
     })
 
     test('rewrites from now past datetime to minutes ago', async () => {
@@ -842,9 +842,25 @@ suite('relative-time', function () {
       assert.equal(time.shadowRoot.textContent, '3 months ago')
     })
 
+    test('does not count an extra year for dates many years in the past', async () => {
+      freezeTime(new Date('2025-02-06T12:00:00Z'))
+      const time = document.createElement('relative-time')
+      time.setAttribute('tense', 'past')
+      time.setAttribute('datetime', '2015-02-14T15:13:48+05:00')
+      await Promise.resolve()
+      assert.equal(time.shadowRoot.textContent, '10 years ago')
+    })
+
+    test('does not count an extra year for exact multiples of five years', async () => {
+      freezeTime(new Date('2025-01-01T00:00:00Z'))
+      const time = document.createElement('relative-time')
+      time.setAttribute('tense', 'past')
+      time.setAttribute('datetime', '2020-01-01T00:00:00Z')
+      await Promise.resolve()
+      assert.equal(time.shadowRoot.textContent, '5 years ago')
+    })
+
     test('micro formats years', async () => {
-      // FIXME: there is still a bug, if the duration is long enough (say, 10 or 100 years)
-      // then the `month = Math.floor(day / 30)` in elapsedTime causes errors, then "10 years" would output "11y"
       const now = new Date(Date.now() - 2 * 365 * 24 * 60 * 60 * 1000).toISOString()
       const time = document.createElement('relative-time')
       time.setAttribute('tense', 'past')
@@ -946,8 +962,6 @@ suite('relative-time', function () {
     })
 
     test('micro formats years', async () => {
-      // FIXME: there is still a bug, if the duration is long enough (say, 10 or 100 years)
-      // then the `month = Math.floor(day / 30)` in elapsedTime causes errors, then "10 years" would output "11y"
       const now = new Date(Date.now() + 2 * 365 * 24 * 60 * 60 * 1000).toISOString()
       const time = document.createElement('relative-time')
       time.setAttribute('tense', 'future')
@@ -1684,7 +1698,7 @@ suite('relative-time', function () {
       {
         datetime: '2024-10-24T14:46:00.000Z',
         format: 'duration',
-        expected: '2 years, 11 days',
+        expected: '2 years',
       },
       {
         datetime: '2024-10-24T14:46:00.000Z',
@@ -1696,19 +1710,19 @@ suite('relative-time', function () {
         datetime: '2024-10-24T14:46:00.000Z',
         format: 'duration',
         precision: 'minute',
-        expected: '2 years, 11 days',
+        expected: '2 years',
       },
       {
         datetime: '2024-10-24T14:46:00.000Z',
         format: 'duration',
         precision: 'day',
-        expected: '2 years, 11 days',
+        expected: '2 years',
       },
       {
         datetime: '2024-10-24T14:46:00.000Z',
         format: 'duration',
         tense: 'future',
-        expected: '2 years, 11 days',
+        expected: '2 years',
       },
       {
         datetime: '2024-10-24T14:46:00.000Z',
@@ -2140,19 +2154,19 @@ suite('relative-time', function () {
       {
         datetime: '2020-10-24T14:46:00.000Z',
         format: 'duration',
-        expected: '2 years, 10 days',
+        expected: '2 years',
       },
       {
         datetime: '2020-10-24T14:46:00.000Z',
         format: 'duration',
         precision: 'minute',
-        expected: '2 years, 10 days',
+        expected: '2 years',
       },
       {
         datetime: '2020-10-24T14:46:00.000Z',
         format: 'duration',
         precision: 'day',
-        expected: '2 years, 10 days',
+        expected: '2 years',
       },
       {
         datetime: '2020-10-24T14:46:00.000Z',
@@ -2164,7 +2178,7 @@ suite('relative-time', function () {
         datetime: '2020-10-24T14:46:00.000Z',
         format: 'duration',
         tense: 'past',
-        expected: '2 years, 10 days',
+        expected: '2 years',
       },
       {
         reference: '2023-03-23T12:03:00.000Z',