diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
index 8619a96b9..d0b7f3cb3 100644
--- a/polyfill/lib/ecmascript.mjs
+++ b/polyfill/lib/ecmascript.mjs
@@ -2098,13 +2098,38 @@ export function GetPossibleEpochNanoseconds(timeZone, isoDateTime) {
   const { year, month, day, hour, minute, second, millisecond, microsecond, nanosecond } = isoDateTime;
   const offsetMinutes = ParseTimeZoneIdentifier(timeZone).offsetMinutes;
   if (offsetMinutes !== undefined) {
-    return [
-      GetUTCEpochNanoseconds(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond).subtract(
-        offsetMinutes * 60e9
-      )
-    ];
+    const balanced = BalanceISODateTime(
+      year,
+      month,
+      day,
+      hour,
+      minute - offsetMinutes,
+      second,
+      millisecond,
+      microsecond,
+      nanosecond
+    );
+    if (MathAbs(ISODateToEpochDays(balanced.year, balanced.month - 1, balanced.day)) > 1e8) {
+      throw new RangeErrorCtor('date/time value is outside the supported range');
+    }
+    const epochNs = GetUTCEpochNanoseconds(
+      balanced.year,
+      balanced.month,
+      balanced.day,
+      balanced.hour,
+      balanced.minute,
+      balanced.second,
+      balanced.millisecond,
+      balanced.microsecond,
+      balanced.nanosecond
+    );
+    ValidateEpochNanoseconds(epochNs);
+    return [epochNs];
   }
 
+  if (MathAbs(ISODateToEpochDays(year, month - 1, day)) > 1e8) {
+    throw new RangeErrorCtor('date/time value is outside the supported range');
+  }
   return GetNamedTimeZoneEpochNanoseconds(
     timeZone,
     year,
@@ -2693,6 +2718,7 @@ export function GetNamedTimeZoneEpochNanoseconds(
       ) {
         return undefined;
       }
+      ValidateEpochNanoseconds(epochNanoseconds);
       return epochNanoseconds;
     }
   ]);
diff --git a/spec/timezone.html b/spec/timezone.html
index 07dbb5f9f..c22315fd9 100644
--- a/spec/timezone.html
+++ b/spec/timezone.html
@@ -357,10 +357,12 @@ <h1>
       <emu-alg>
         1. Let _parseResult_ be ! ParseTimeZoneIdentifier(_timeZone_).
         1. If _parseResult_.[[OffsetMinutes]] is not ~empty~, then
-          1. Let _offsetNanoseconds_ be _parseResult_.[[OffsetMinutes]] × (60 × 10<sup>9</sup>).
-          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_isoDateTime_.[[Year]], _isoDateTime_.[[Month]], _isoDateTime_.[[Day]], _isoDateTime_.[[Hour]], _isoDateTime_.[[Minute]], _isoDateTime_.[[Second]], _isoDateTime_.[[Millisecond]], _isoDateTime_.[[Microsecond]], _isoDateTime_.[[Nanosecond]]) - ℤ(_offsetNanoseconds_).
+          1. Let _balanced_ be BalanceISODateTime(_isoDateTime_.[[Year]], _isoDateTime_.[[Month]], _isoDateTime_.[[Day]], _isoDateTime_.[[Hour]], _isoDateTime_.[[Minute]] - _parseResult_.[[OffsetMinutes]], _isoDateTime_.[[Second]], _isoDateTime_.[[Millisecond]], _isoDateTime_.[[Microsecond]], _isoDateTime_.[[Nanosecond]]).
+          1. If abs(ISODateToEpochDays(_balanced_.[[Year]], _balanced_.[[Month]] - 1, _balanced_.[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_.[[Year]], _balanced_.[[Month]], _balanced_.[[Day]], _balanced_.[[Hour]], _balanced_.[[Minute]], _balanced_.[[Second]], _balanced_.[[Millisecond]], _balanced_.[[Microsecond]], _balanced_.[[Nanosecond]]).
           1. Let _possibleEpochNanoseconds_ be « _epochNanoseconds_ ».
         1. Else,
+          1. If abs(ISODateToEpochDays(_isoDateTime_.[[Year]], _isoDateTime_.[[Month]] - 1, _isoDateTime_.[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
           1. Let _possibleEpochNanoseconds_ be GetNamedTimeZoneEpochNanoseconds(_parseResult_.[[Name]], _isoDateTime_.[[Year]], _isoDateTime_.[[Month]], _isoDateTime_.[[Day]], _isoDateTime_.[[Hour]], _isoDateTime_.[[Minute]], _isoDateTime_.[[Second]], _isoDateTime_.[[Millisecond]], _isoDateTime_.[[Microsecond]], _isoDateTime_.[[Nanosecond]]).
         1. For each value _epochNanoseconds_ in _possibleEpochNanoseconds_, do
           1. If IsValidEpochNanoseconds(_epochNanoseconds_) is *false*, throw a *RangeError* exception.