diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
index 12ce550562..9c48b6eb23 100644
--- a/polyfill/lib/ecmascript.mjs
+++ b/polyfill/lib/ecmascript.mjs
@@ -1153,6 +1153,13 @@ export const ES = ObjectAssign({}, ES2020, {
   ToTemporalDate: (item, options = {}) => {
     if (ES.Type(item) === 'Object') {
       if (ES.IsTemporalDate(item)) return item;
+      if (ES.IsTemporalZonedDateTime(item)) {
+        item = ES.BuiltinTimeZoneGetPlainDateTimeFor(
+          GetSlot(item, TIME_ZONE),
+          GetSlot(item, INSTANT),
+          GetSlot(item, CALENDAR)
+        );
+      }
       if (ES.IsTemporalDateTime(item)) {
         const TemporalPlainDate = GetIntrinsic('%Temporal.PlainDate%');
         return new TemporalPlainDate(
@@ -1197,6 +1204,13 @@ export const ES = ObjectAssign({}, ES2020, {
     let year, month, day, hour, minute, second, millisecond, microsecond, nanosecond, calendar;
     if (ES.Type(item) === 'Object') {
       if (ES.IsTemporalDateTime(item)) return item;
+      if (ES.IsTemporalZonedDateTime(item)) {
+        return ES.BuiltinTimeZoneGetPlainDateTimeFor(
+          GetSlot(item, TIME_ZONE),
+          GetSlot(item, INSTANT),
+          GetSlot(item, CALENDAR)
+        );
+      }
       if (ES.IsTemporalDate(item)) {
         const TemporalPlainDateTime = GetIntrinsic('%Temporal.PlainDateTime%');
         return new TemporalPlainDateTime(
@@ -1354,6 +1368,13 @@ export const ES = ObjectAssign({}, ES2020, {
     let hour, minute, second, millisecond, microsecond, nanosecond, calendar;
     if (ES.Type(item) === 'Object') {
       if (ES.IsTemporalTime(item)) return item;
+      if (ES.IsTemporalZonedDateTime(item)) {
+        item = ES.BuiltinTimeZoneGetPlainDateTimeFor(
+          GetSlot(item, TIME_ZONE),
+          GetSlot(item, INSTANT),
+          GetSlot(item, CALENDAR)
+        );
+      }
       if (ES.IsTemporalDateTime(item)) {
         const TemporalPlainTime = GetIntrinsic('%Temporal.PlainTime%');
         return new TemporalPlainTime(
diff --git a/spec/plaindate.html b/spec/plaindate.html
index ff1428ad4c..1a986c311d 100644
--- a/spec/plaindate.html
+++ b/spec/plaindate.html
@@ -676,6 +676,10 @@ <h1>ToTemporalDate ( _item_ [ , _options_ ] )</h1>
         1. If Type(_item_) is Object, then
           1. If _item_ has an [[InitializedTemporalDate]] internal slot, then
             1. Return _item_.
+          1. If _item_ has an [[InitializedTemporalZonedDateTime]] internal slot, then
+            1. Let _instant_ be ! CreateTemporalInstant(_item_.[[Nanoseconds]]).
+            1. Let _plainDateTime_ be ? BuiltinTimeZoneGetPlainDateTimeFor(_item_.[[TimeZone]], _instant_, _item_.[[Calendar]]).
+            1. Return ! CreateTemporalDate(_plainDateTime_.[[ISOYear]], _plainDateTime_.[[ISOMonth]], _plainDateTime_.[[ISODay]], _plainDateTime_.[[Calendar]]).
           1. If _item_ has an [[InitializedTemporalDateTime]] internal slot, then
             1. Return ! CreateTemporalDate(_item_.[[ISOYear]], _item_.[[ISOMonth]], _item_.[[ISODay]], _item_.[[Calendar]]).
           1. Let _calendar_ be ? GetOptionalTemporalCalendar(_item_).
diff --git a/spec/plaindatetime.html b/spec/plaindatetime.html
index d172d41f1b..4b91c02a8c 100644
--- a/spec/plaindatetime.html
+++ b/spec/plaindatetime.html
@@ -903,6 +903,9 @@ <h1>ToTemporalDateTime ( _item_ [ , _options_ ] )</h1>
         1. If Type(_item_) is Object, then
           1. If _item_ has an [[InitializedTemporalDateTime]] internal slot, then
             1. Return _item_.
+          1. If _item_ has an [[InitializedTemporalZonedDateTime]] internal slot, then
+            1. Let _instant_ be ! CreateTemporalInstant(_item_.[[Nanoseconds]]).
+            1. Return ? BuiltinTimeZoneGetPlainDateTimeFor(_item_.[[TimeZone]], _instant_, _item_.[[Calendar]]).
           1. If _item_ has an [[InitializedTemporalDate]] internal slot, then
             1. Return ? CreateTemporalDateTime(_item_.[[ISOYear]], _item_.[[ISOMonth]], _item_.[[ISODay]], 0, 0, 0, 0, 0, 0, _item_.[[Calendar]]).
           1. Let _calendar_ be ? GetOptionalTemporalCalendar(_item_).
diff --git a/spec/plaintime.html b/spec/plaintime.html
index ef97e208cf..f43f1bdd10 100644
--- a/spec/plaintime.html
+++ b/spec/plaintime.html
@@ -610,6 +610,10 @@ <h1>ToTemporalTime ( _item_ [ , _overflow_ ] )</h1>
         1. If Type(_item_) is Object, then
           1. If _item_ has an [[InitializedTemporalTime]] internal slot, then
             1. Return _item_.
+          1. If _item_ has an [[InitializedTemporalZonedDateTime]] internal slot, then
+            1. Let _instant_ be ? CreateTemporalInstant(_item_.[[Nanoseconds]]).
+            1. Set _plainDateTime_ to ? BuiltinTimeZoneGetPlainDateTimeFor(_item_.[[TimeZone]], _instant_, _item_.[[Calendar]]).
+            1. Return ! CreateTemporalTime(_plainDateTime_.[[ISOHour]], _plainDateTime_.[[ISOMinute]], _plainDateTime_.[[ISOSecond]], _plainDateTime_.[[ISOMillisecond]], _plainDateTime_.[[ISOMicrosecond]], _plainDateTime_.[[ISONanosecond]]).
           1. If _item_ has an [[InitializedTemporalDateTime]] internal slot, then
             1. Return ! CreateTemporalTime(_item_.[[ISOHour]], _item_.[[ISOMinute]], _item_.[[ISOSecond]], _item_.[[ISOMillisecond]], _item_.[[ISOMicrosecond]], _item_.[[ISONanosecond]]).
           1. Let _calendar_ be ? GetOptionalTemporalCalendar(_item_).