diff --git a/src/duration.ts b/src/duration.ts
index d0d4781..7098bc9 100644
--- a/src/duration.ts
+++ b/src/duration.ts
@@ -130,28 +130,25 @@ export function roundToSingleUnit(duration: Duration): Duration {
   let seconds = Math.abs(duration.seconds)
   let milliseconds = Math.abs(duration.milliseconds)
 
-  if (milliseconds >= 500) seconds += Math.round(milliseconds / 1000)
+  if (milliseconds >= 900) seconds += Math.round(milliseconds / 1000)
   if (seconds || minutes || hours || days || weeks || months || years) milliseconds = 0
 
-  if (seconds >= 30) minutes += Math.round(seconds / 60)
+  if (seconds >= 55) minutes += Math.round(seconds / 60)
   if (minutes || hours || days || weeks || months || years) seconds = 0
 
-  if (minutes >= 30) hours += Math.round(minutes / 60)
+  if (minutes >= 55) hours += Math.round(minutes / 60)
   if (hours || days || weeks || months || years) minutes = 0
 
-  if (hours >= 12) days += Math.round(hours / 24)
+  if (hours >= 21) days += Math.round(hours / 24)
   if (days || weeks || months || years) hours = 0
 
-  if (days >= 15) months += Math.round(days / 30)
+  if (days >= 6) weeks += Math.round(days / 7)
   if (weeks || months || years) days = 0
 
-  if (days >= 4) weeks += Math.round(days / 7)
-  if (weeks || months || years) days = 0
-
-  if (weeks >= 2) months += Math.round(weeks / 4)
+  if (weeks >= 4) months += Math.round(weeks / 4)
   if (months || years) weeks = 0
 
-  if (months >= 6) years += Math.round(months / 12)
+  if (months >= 11) years += Math.round(months / 12)
   if (years) months = 0
 
   const sign = duration.sign
diff --git a/test/duration.ts b/test/duration.ts
index d55c247..82c0c9f 100644
--- a/test/duration.ts
+++ b/test/duration.ts
@@ -124,19 +124,35 @@ suite('duration', function () {
   suite('roundToSingleUnit', function () {
     const roundTests = new Set([
       ['PT20S', 'PT20S'],
-      ['PT31S', 'PT1M'],
+      ['PT31S', 'PT31S'],
+      ['PT55S', 'PT1M'],
       ['PT1H', 'PT1H'],
       ['PT1H14M', 'PT1H'],
       ['PT1H29M', 'PT1H'],
-      ['PT1H31M', 'PT2H'],
-      ['PT1H45M', 'PT2H'],
+      ['PT1H31M', 'PT1H'],
+      ['PT1H55M', 'PT2H'],
+      ['PT20H', 'PT20H'],
+      ['PT21H', 'P1D'],
+      ['P4D', 'P4D'],
       ['P6D', 'P1W'],
+      ['P2W', 'P2W'],
+      ['P3W3D', 'P3W'],
+      ['P3W6D', 'P1M'],
+      ['P21D', 'P3W'],
+      ['P24D', 'P3W'],
+      ['P24DT25H', 'P1M'],
+      ['P25D', 'P1M'],
+      ['P8M', 'P8M'],
+      ['P9M', 'P9M'],
       ['P1M1D', 'P1M'],
+      ['P9M20DT25H', 'P9M'],
+      ['P9M24DT25H', 'P10M'],
+      ['P11M', 'P1Y'],
       ['P1Y4D', 'P1Y'],
       ['P1Y5M13D', 'P1Y'],
-      ['P1Y5M15D', 'P2Y'],
-      ['P1Y5M20D', 'P2Y'],
-      ['P1Y6M', 'P2Y'],
+      ['P1Y5M15D', 'P1Y'],
+      ['P1Y5M20D', 'P1Y'],
+      ['P1Y11M', 'P2Y'],
     ])
     for (const [input, expected] of roundTests) {
       test(`roundToSingleUnit(${input}) === ${expected}`, () => {
@@ -151,19 +167,35 @@ suite('duration', function () {
   suite('getRelativeTimeUnit', function () {
     const relativeTests = new Set([
       ['PT20S', [20, 'second']],
-      ['PT31S', [1, 'minute']],
+      ['PT31S', [31, 'second']],
+      ['PT55S', [1, 'minute']],
       ['PT1H', [1, 'hour']],
       ['PT1H14M', [1, 'hour']],
       ['PT1H29M', [1, 'hour']],
-      ['PT1H31M', [2, 'hour']],
-      ['PT1H45M', [2, 'hour']],
+      ['PT1H31M', [1, 'hour']],
+      ['PT1H55M', [2, 'hour']],
+      ['PT20H', [20, 'hour']],
+      ['PT21H', [1, 'day']],
+      ['P4D', [4, 'day']],
       ['P6D', [1, 'week']],
+      ['P2W', [2, 'week']],
+      ['P3W3D', [3, 'week']],
+      ['P3W6D', [1, 'month']],
+      ['P21D', [3, 'week']],
+      ['P24D', [3, 'week']],
+      ['P24DT25H', [1, 'month']],
+      ['P25D', [1, 'month']],
+      ['P8M', [8, 'month']],
+      ['P9M', [9, 'month']],
       ['P1M1D', [1, 'month']],
+      ['P9M20DT25H', [9, 'month']],
+      ['P9M24DT25H', [10, 'month']],
+      ['P11M', [1, 'year']],
       ['P1Y4D', [1, 'year']],
       ['P1Y5M13D', [1, 'year']],
-      ['P1Y5M15D', [2, 'year']],
-      ['P1Y5M20D', [2, 'year']],
-      ['P1Y6M', [2, 'year']],
+      ['P1Y5M15D', [1, 'year']],
+      ['P1Y5M20D', [1, 'year']],
+      ['P1Y11M', [2, 'year']],
     ])
     for (const [input, [val, unit]] of relativeTests) {
       test(`roundToSingleUnit(${input}) === [${val}, ${unit}]`, () => {
diff --git a/test/relative-time.js b/test/relative-time.js
index 849b8b2..ed37606 100644
--- a/test/relative-time.js
+++ b/test/relative-time.js
@@ -472,7 +472,7 @@ suite('relative-time', function () {
       timeElement.setAttribute('tense', 'past')
       timeElement.setAttribute('datetime', then)
       await Promise.resolve()
-      assert.equal(timeElement.shadowRoot.textContent, '2 years ago')
+      assert.equal(timeElement.shadowRoot.textContent, 'last year')
     })
 
     test('micro formats years', async () => {
@@ -762,9 +762,9 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T14:46:08.000Z', format: 'duration', tense: 'past', expected: '0 seconds'},
 
       // 50 seconds in the future
-      {datetime: '2022-10-24T14:46:50.000Z', tense: 'future', format: 'relative', expected: 'in 1 minute'},
+      {datetime: '2022-10-24T14:46:50.000Z', tense: 'future', format: 'relative', expected: 'in 50 seconds'},
       {datetime: '2022-10-24T14:46:50.000Z', tense: 'past', format: 'relative', expected: 'now'},
-      {datetime: '2022-10-24T14:46:50.000Z', format: 'relative', formatStyle: 'narrow', expected: 'in 1 min.'},
+      {datetime: '2022-10-24T14:46:50.000Z', format: 'relative', formatStyle: 'narrow', expected: 'in 50 sec.'},
       {datetime: '2022-10-24T14:46:50.000Z', format: 'relative', precision: 'hour', expected: 'now'},
       {datetime: '2022-10-24T14:46:50.000Z', format: 'relative', threshold: 'PT0S', expected: 'on Oct 24'},
       {datetime: '2022-10-24T14:46:50.000Z', format: 'datetime', expected: 'Mon, Oct 24'},
@@ -775,9 +775,9 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T14:46:50.000Z', format: 'duration', tense: 'past', expected: '0 seconds'},
 
       // 90 seconds in the future
-      {datetime: '2022-10-24T14:47:30.000Z', tense: 'future', format: 'relative', expected: 'in 2 minutes'},
+      {datetime: '2022-10-24T14:47:30.000Z', tense: 'future', format: 'relative', expected: 'in 1 minute'},
       {datetime: '2022-10-24T14:47:30.000Z', tense: 'past', format: 'relative', expected: 'now'},
-      {datetime: '2022-10-24T14:47:30.000Z', format: 'relative', formatStyle: 'narrow', expected: 'in 2 min.'},
+      {datetime: '2022-10-24T14:47:30.000Z', format: 'relative', formatStyle: 'narrow', expected: 'in 1 min.'},
       {datetime: '2022-10-24T14:47:30.000Z', format: 'relative', precision: 'hour', expected: 'now'},
       {datetime: '2022-10-24T14:47:30.000Z', format: 'relative', threshold: 'PT0S', expected: 'on Oct 24'},
       {datetime: '2022-10-24T14:47:30.000Z', format: 'datetime', expected: 'Mon, Oct 24'},
@@ -788,10 +788,10 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T14:47:30.000Z', format: 'duration', tense: 'past', expected: '0 seconds'},
 
       // 20 days in the future
-      {datetime: '2022-11-13T15:46:00.000Z', tense: 'future', format: 'relative', expected: 'next month'},
+      {datetime: '2022-11-13T15:46:00.000Z', tense: 'future', format: 'relative', expected: 'in 3 weeks'},
       {datetime: '2022-11-13T15:46:00.000Z', tense: 'past', format: 'relative', expected: 'now'},
-      {datetime: '2022-11-13T15:46:00.000Z', format: 'relative', formatStyle: 'narrow', expected: 'next mo.'},
-      {datetime: '2022-11-13T15:46:00.000Z', format: 'relative', precision: 'hour', expected: 'next month'},
+      {datetime: '2022-11-13T15:46:00.000Z', format: 'relative', formatStyle: 'narrow', expected: 'in 3 wk.'},
+      {datetime: '2022-11-13T15:46:00.000Z', format: 'relative', precision: 'hour', expected: 'in 3 weeks'},
       {datetime: '2022-11-13T15:46:00.000Z', format: 'relative', threshold: 'PT0S', expected: 'on Nov 13'},
       {datetime: '2022-11-13T15:46:00.000Z', format: 'datetime', expected: 'Sun, Nov 13'},
       {datetime: '2022-11-13T15:46:00.000Z', format: 'duration', expected: '20 days, 1 hour'},
@@ -846,8 +846,8 @@ suite('relative-time', function () {
 
       // 50 seconds in the past
       {datetime: '2022-10-24T14:45:10.000Z', tense: 'future', format: 'relative', expected: 'now'},
-      {datetime: '2022-10-24T14:45:10.000Z', tense: 'past', format: 'relative', expected: '1 minute ago'},
-      {datetime: '2022-10-24T14:45:10.000Z', format: 'relative', formatStyle: 'narrow', expected: '1 min. ago'},
+      {datetime: '2022-10-24T14:45:10.000Z', tense: 'past', format: 'relative', expected: 'now'},
+      {datetime: '2022-10-24T14:45:10.000Z', format: 'relative', formatStyle: 'narrow', expected: 'now'},
       {datetime: '2022-10-24T14:45:10.000Z', format: 'relative', precision: 'hour', expected: 'now'},
       {datetime: '2022-10-24T14:45:10.000Z', format: 'relative', threshold: 'PT0S', expected: 'on Oct 24'},
       {datetime: '2022-10-24T14:45:10.000Z', format: 'datetime', expected: 'Mon, Oct 24'},
@@ -859,8 +859,8 @@ suite('relative-time', function () {
 
       // 90 seconds in the past
       {datetime: '2022-10-24T14:44:30.000Z', tense: 'future', format: 'relative', expected: 'now'},
-      {datetime: '2022-10-24T14:44:30.000Z', tense: 'past', format: 'relative', expected: '2 minutes ago'},
-      {datetime: '2022-10-24T14:44:30.000Z', format: 'relative', formatStyle: 'narrow', expected: '2 min. ago'},
+      {datetime: '2022-10-24T14:44:30.000Z', tense: 'past', format: 'relative', expected: '1 minute ago'},
+      {datetime: '2022-10-24T14:44:30.000Z', format: 'relative', formatStyle: 'narrow', expected: '1 min. ago'},
       {datetime: '2022-10-24T14:44:30.000Z', format: 'relative', precision: 'hour', expected: 'now'},
       {datetime: '2022-10-24T14:44:30.000Z', format: 'relative', threshold: 'PT0S', expected: 'on Oct 24'},
       {datetime: '2022-10-24T14:44:30.000Z', format: 'datetime', expected: 'Mon, Oct 24'},
@@ -872,9 +872,9 @@ suite('relative-time', function () {
 
       // 20 days in the past
       {datetime: '2022-10-04T14:46:00.000Z', tense: 'future', format: 'relative', expected: 'now'},
-      {datetime: '2022-10-04T14:46:00.000Z', tense: 'past', format: 'relative', expected: 'last month'},
-      {datetime: '2022-10-04T14:46:00.000Z', format: 'relative', formatStyle: 'narrow', expected: 'last mo.'},
-      {datetime: '2022-10-04T14:46:00.000Z', format: 'relative', precision: 'hour', expected: 'last month'},
+      {datetime: '2022-10-04T14:46:00.000Z', tense: 'past', format: 'relative', expected: '3 weeks ago'},
+      {datetime: '2022-10-04T14:46:00.000Z', format: 'relative', formatStyle: 'narrow', expected: '3 wk. ago'},
+      {datetime: '2022-10-04T14:46:00.000Z', format: 'relative', precision: 'hour', expected: '3 weeks ago'},
       {datetime: '2022-10-04T14:46:00.000Z', format: 'relative', threshold: 'PT0S', expected: 'on Oct 4'},
       {datetime: '2022-10-04T14:46:00.000Z', format: 'datetime', expected: 'Tue, Oct 4'},
       {datetime: '2022-10-04T14:46:00.000Z', format: 'duration', expected: '20 days'},
@@ -958,13 +958,13 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T15:46:00.000Z', tense: 'future', format: 'micro', expected: '1h'},
       {datetime: '2022-10-24T16:00:00.000Z', tense: 'future', format: 'micro', expected: '1h'},
       {datetime: '2022-10-24T16:15:00.000Z', tense: 'future', format: 'micro', expected: '1h'},
-      {datetime: '2022-10-24T16:31:00.000Z', tense: 'future', format: 'micro', expected: '2h'},
+      {datetime: '2022-10-24T16:31:00.000Z', tense: 'future', format: 'micro', expected: '1h'},
       {datetime: '2022-10-30T14:46:00.000Z', tense: 'future', format: 'micro', expected: '1w'},
       {datetime: '2022-11-24T14:46:00.000Z', tense: 'future', format: 'micro', expected: '1m'},
       {datetime: '2023-10-23T14:46:00.000Z', tense: 'future', format: 'micro', expected: '1y'},
       {datetime: '2023-10-24T14:46:00.000Z', tense: 'future', format: 'micro', expected: '1y'},
       {datetime: '2024-03-31T14:46:00.000Z', tense: 'future', format: 'micro', expected: '1y'},
-      {datetime: '2024-04-01T14:46:00.000Z', tense: 'future', format: 'micro', expected: '2y'},
+      {datetime: '2024-04-01T14:46:00.000Z', tense: 'future', format: 'micro', expected: '1y'},
 
       // Dates in the future
       {datetime: '2022-11-24T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1m'},
@@ -975,13 +975,13 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T13:46:00.000Z', tense: 'past', format: 'micro', expected: '1h'},
       {datetime: '2022-10-24T13:30:00.000Z', tense: 'past', format: 'micro', expected: '1h'},
       {datetime: '2022-10-24T13:17:00.000Z', tense: 'past', format: 'micro', expected: '1h'},
-      {datetime: '2022-10-24T13:01:00.000Z', tense: 'past', format: 'micro', expected: '2h'},
+      {datetime: '2022-10-24T13:01:00.000Z', tense: 'past', format: 'micro', expected: '1h'},
       {datetime: '2022-10-18T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1w'},
       {datetime: '2022-09-23T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1m'},
       {datetime: '2021-10-25T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1y'},
       {datetime: '2021-10-24T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1y'},
       {datetime: '2021-05-18T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1y'},
-      {datetime: '2021-05-17T14:46:00.000Z', tense: 'past', format: 'micro', expected: '2y'},
+      {datetime: '2021-05-17T14:46:00.000Z', tense: 'past', format: 'micro', expected: '1y'},
 
       // Elapsed Times
       {datetime: '2022-10-24T14:46:10.000Z', format: 'elapsed', expected: '10s'},
@@ -1011,23 +1011,23 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T15:46:00.000Z', tense: 'future', format: 'auto', expected: 'in 1 hour'},
       {datetime: '2022-10-24T16:00:00.000Z', tense: 'future', format: 'auto', expected: 'in 1 hour'},
       {datetime: '2022-10-24T16:15:00.000Z', tense: 'future', format: 'auto', expected: 'in 1 hour'},
-      {datetime: '2022-10-24T16:31:00.000Z', tense: 'future', format: 'auto', expected: 'in 2 hours'},
+      {datetime: '2022-10-24T16:31:00.000Z', tense: 'future', format: 'auto', expected: 'in 1 hour'},
       {datetime: '2022-10-30T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'next week'},
       {datetime: '2022-11-24T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'next month'},
       {datetime: '2023-10-23T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'next year'},
       {datetime: '2023-10-24T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'next year'},
       {datetime: '2024-03-31T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'next year'},
-      {datetime: '2024-04-01T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'in 2 years'},
+      {datetime: '2024-04-01T14:46:00.000Z', tense: 'future', format: 'auto', expected: 'next year'},
       {datetime: '2022-10-24T15:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'in 1 hr.'},
       {datetime: '2022-10-24T16:00:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'in 1 hr.'},
       {datetime: '2022-10-24T16:15:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'in 1 hr.'},
-      {datetime: '2022-10-24T16:31:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'in 2 hr.'},
+      {datetime: '2022-10-24T16:31:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'in 1 hr.'},
       {datetime: '2022-10-30T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'next wk.'},
       {datetime: '2022-11-24T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'next mo.'},
       {datetime: '2023-10-23T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'next yr.'},
       {datetime: '2023-10-24T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'next yr.'},
       {datetime: '2024-03-31T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'next yr.'},
-      {datetime: '2024-04-01T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'in 2 yr.'},
+      {datetime: '2024-04-01T14:46:00.000Z', lang: 'en', tense: 'future', formatStyle: 'narrow', expected: 'next yr.'},
 
       // Dates in the future
       {datetime: '2022-11-24T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'now'},
@@ -1038,23 +1038,23 @@ suite('relative-time', function () {
       {datetime: '2022-10-24T13:46:00.000Z', tense: 'past', format: 'auto', expected: '1 hour ago'},
       {datetime: '2022-10-24T13:30:00.000Z', tense: 'past', format: 'auto', expected: '1 hour ago'},
       {datetime: '2022-10-24T13:17:00.000Z', tense: 'past', format: 'auto', expected: '1 hour ago'},
-      {datetime: '2022-10-24T13:01:00.000Z', tense: 'past', format: 'auto', expected: '2 hours ago'},
+      {datetime: '2022-10-24T13:01:00.000Z', tense: 'past', format: 'auto', expected: '1 hour ago'},
       {datetime: '2022-10-18T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'last week'},
       {datetime: '2022-09-23T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'last month'},
       {datetime: '2021-10-25T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'last year'},
       {datetime: '2021-10-24T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'last year'},
       {datetime: '2021-05-18T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'last year'},
-      {datetime: '2021-05-17T14:46:00.000Z', tense: 'past', format: 'auto', expected: '2 years ago'},
+      {datetime: '2021-05-17T14:46:00.000Z', tense: 'past', format: 'auto', expected: 'last year'},
       {datetime: '2022-10-24T13:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: '1 hr. ago'},
       {datetime: '2022-10-24T13:30:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: '1 hr. ago'},
       {datetime: '2022-10-24T13:17:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: '1 hr. ago'},
-      {datetime: '2022-10-24T13:01:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: '2 hr. ago'},
+      {datetime: '2022-10-24T13:01:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: '1 hr. ago'},
       {datetime: '2022-10-18T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: 'last wk.'},
       {datetime: '2022-09-23T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: 'last mo.'},
       {datetime: '2021-10-25T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: 'last yr.'},
       {datetime: '2021-10-24T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: 'last yr.'},
       {datetime: '2021-05-18T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: 'last yr.'},
-      {datetime: '2021-05-17T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: '2 yr. ago'},
+      {datetime: '2021-05-17T14:46:00.000Z', lang: 'en', tense: 'past', formatStyle: 'narrow', expected: 'last yr.'},
 
       // Edge case dates
       {