diff --git a/build/autoconf/icu.m4 b/build/autoconf/icu.m4
index 49896cae9a7c..6afa262b073e 100644
--- a/build/autoconf/icu.m4
+++ b/build/autoconf/icu.m4
@@ -14,7 +14,7 @@ MOZ_ARG_WITH_BOOL(system-icu,
     MOZ_SYSTEM_ICU=1)
 
 if test -n "$MOZ_SYSTEM_ICU"; then
-    PKG_CHECK_MODULES(MOZ_ICU, icu-i18n >= 64.1)
+    PKG_CHECK_MODULES(MOZ_ICU, icu-i18n >= 63.1)
     CFLAGS="$CFLAGS $MOZ_ICU_CFLAGS"
     CXXFLAGS="$CXXFLAGS $MOZ_ICU_CFLAGS"
     AC_DEFINE(MOZ_SYSTEM_ICU)
diff --git a/config/check_spidermonkey_style.py b/config/check_spidermonkey_style.py
index 11e80abc8499..9df1e412bcfa 100644
--- a/config/check_spidermonkey_style.py
+++ b/config/check_spidermonkey_style.py
@@ -97,7 +97,6 @@ included_inclnames_to_ignore = set([
     'unicode/udatpg.h',         # ICU
     'unicode/udisplaycontext.h',  # ICU
     'unicode/uenum.h',          # ICU
-    'unicode/uformattedvalue.h',  # ICU
     'unicode/uloc.h',           # ICU
     'unicode/unistr.h',         # ICU
     'unicode/unorm2.h',         # ICU
diff --git a/config/system-headers.mozbuild b/config/system-headers.mozbuild
index 0af5e2afe22c..bcf5c4925564 100644
--- a/config/system-headers.mozbuild
+++ b/config/system-headers.mozbuild
@@ -1330,7 +1330,6 @@ if CONFIG['MOZ_SYSTEM_ICU']:
         'unicode/udatpg.h',
         'unicode/udisplaycontext.h',
         'unicode/uenum.h',
-        'unicode/uformattedvalue.h',
         'unicode/unistr.h',
         'unicode/unorm.h',
         'unicode/unum.h',
diff --git a/js/src/builtin/intl/DateTimeFormat.cpp b/js/src/builtin/intl/DateTimeFormat.cpp
index 409078821593..fea9ed385c3c 100644
--- a/js/src/builtin/intl/DateTimeFormat.cpp
+++ b/js/src/builtin/intl/DateTimeFormat.cpp
@@ -946,13 +946,10 @@ bool js::intl_FormatDateTime(JSContext* cx, unsigned argc, Value* vp) {
   Rooted<DateTimeFormatObject*> dateTimeFormat(cx);
   dateTimeFormat = &args[0].toObject().as<DateTimeFormatObject>();
 
-  bool formatToParts = args[2].toBoolean();
-
   ClippedTime x = TimeClip(args[1].toNumber());
   if (!x.isValid()) {
     JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
-                              JSMSG_DATE_NOT_FINITE, "DateTimeFormat",
-                              formatToParts ? "formatToParts" : "format");
+                              JSMSG_DATE_NOT_FINITE, "DateTimeFormat");
     return false;
   }
 
@@ -971,6 +968,7 @@ bool js::intl_FormatDateTime(JSContext* cx, unsigned argc, Value* vp) {
   }
 
   // Use the UDateFormat to actually format the time stamp.
-  return formatToParts ? intl_FormatToPartsDateTime(cx, df, x, args.rval())
-                       : intl_FormatDateTime(cx, df, x, args.rval());
+  return args[2].toBoolean()
+             ? intl_FormatToPartsDateTime(cx, df, x, args.rval())
+             : intl_FormatDateTime(cx, df, x, args.rval());
 }
diff --git a/js/src/builtin/intl/ICUStubs.h b/js/src/builtin/intl/ICUStubs.h
index f7e3f586c5d5..6272bf056b62 100644
--- a/js/src/builtin/intl/ICUStubs.h
+++ b/js/src/builtin/intl/ICUStubs.h
@@ -28,7 +28,6 @@
 #  include "unicode/udatpg.h"
 #  include "unicode/udisplaycontext.h"
 #  include "unicode/uenum.h"
-#  include "unicode/uformattedvalue.h"
 #  include "unicode/uloc.h"
 #  include "unicode/unum.h"
 #  include "unicode/unumsys.h"
@@ -47,6 +46,8 @@
 
 #if !ENABLE_INTL_API
 
+#  define U_ICU_VERSION_MAJOR_NUM 64
+
 enum UErrorCode {
   U_ZERO_ERROR,
   U_BUFFER_OVERFLOW_ERROR,
@@ -673,74 +674,6 @@ inline int32_t ureldatefmt_formatNumeric(
   MOZ_CRASH("ureldatefmt_formatNumeric: Intl API disabled");
 }
 
-struct UFormattedRelativeDateTime;
-
-inline UFormattedRelativeDateTime* ureldatefmt_openResult(UErrorCode* status) {
-  MOZ_CRASH("ureldatefmt_openResult: Intl API disabled");
-}
-
-inline void ureldatefmt_closeResult(UFormattedRelativeDateTime* ufrdt) {
-  MOZ_CRASH("ureldatefmt_closeResult: Intl API disabled");
-}
-
-inline void ureldatefmt_formatToResult(
-    const URelativeDateTimeFormatter* reldatefmt, double offset,
-    URelativeDateTimeUnit unit, UFormattedRelativeDateTime* result,
-    UErrorCode* status) {
-  MOZ_CRASH("ureldatefmt_formatToResult: Intl API disabled");
-}
-
-inline void ureldatefmt_formatNumericToResult(
-    const URelativeDateTimeFormatter* reldatefmt, double offset,
-    URelativeDateTimeUnit unit, UFormattedRelativeDateTime* result,
-    UErrorCode* status) {
-  MOZ_CRASH("ureldatefmt_formatToResult: Intl API disabled");
-}
-
-struct UFormattedValue;
-
-inline const UFormattedValue* ureldatefmt_resultAsValue(
-    const UFormattedRelativeDateTime* ufrdt, UErrorCode* status) {
-  MOZ_CRASH("ureldatefmt_resultAsValue: Intl API disabled");
-}
-
-inline const UChar* ufmtval_getString(const UFormattedValue* ufmtval,
-                                      int32_t* pLength, UErrorCode* status) {
-  MOZ_CRASH("ufmtval_getString: Intl API disabled");
-}
-
-inline UConstrainedFieldPosition* ucfpos_open(UErrorCode* status) {
-  MOZ_CRASH("ucfpos_open: Intl API disabled");
-}
-
-inline void ucfpos_close(UConstrainedFieldPosition* ucfpos) {
-  MOZ_CRASH("ucfpos_close: Intl API disabled");
-}
-
-typedef enum UFieldCategory { UFIELD_CATEGORY_NUMBER } UFieldCategory;
-
-inline void ucfpos_constrainCategory(UConstrainedFieldPosition* ucfpos,
-                                     int32_t category, UErrorCode* status) {
-  MOZ_CRASH("ucfpos_constrainCategory: Intl API disabled");
-}
-
-inline bool ufmtval_nextPosition(const UFormattedValue* ufmtval,
-                                 UConstrainedFieldPosition* ucfpos,
-                                 UErrorCode* status) {
-  MOZ_CRASH("ufmtval_nextPosition: Intl API disabled");
-}
-
-inline int32_t ucfpos_getField(const UConstrainedFieldPosition* ucfpos,
-                               UErrorCode* status) {
-  MOZ_CRASH("ucfpos_getField: Intl API disabled");
-}
-
-inline void ucfpos_getIndexes(const UConstrainedFieldPosition* ucfpos,
-                              int32_t* pStart, int32_t* pLimit,
-                              UErrorCode* status) {
-  MOZ_CRASH("ucfpos_getIndexes: Intl API disabled");
-}
-
 #endif  // !ENABLE_INTL_API
 
 #endif /* builtin_intl_ICUStubs_h */
diff --git a/js/src/builtin/intl/NumberFormat.cpp b/js/src/builtin/intl/NumberFormat.cpp
index f0a03dc0d5bb..7b49dec41899 100644
--- a/js/src/builtin/intl/NumberFormat.cpp
+++ b/js/src/builtin/intl/NumberFormat.cpp
@@ -433,8 +433,10 @@ static bool intl_FormatNumber(JSContext* cx, UNumberFormat* nf, double x,
   return true;
 }
 
-static intl::FieldType GetFieldTypeForNumberField(UNumberFormatFields fieldName,
-                                                  double d) {
+using FieldType = ImmutablePropertyNamePtr JSAtomState::*;
+
+static FieldType GetFieldTypeForNumberField(UNumberFormatFields fieldName,
+                                            double d) {
   // See intl/icu/source/i18n/unicode/unum.h for a detailed field list.  This
   // list is deliberately exhaustive: cases might have to be added/removed if
   // this code is compiled with a different ICU with more UNumberFormatFields
@@ -494,6 +496,7 @@ static intl::FieldType GetFieldTypeForNumberField(UNumberFormatFields fieldName,
       break;
 
 #ifndef U_HIDE_DRAFT_API
+#  if U_ICU_VERSION_MAJOR_NUM >= 64
     case UNUM_MEASURE_UNIT_FIELD:
       MOZ_ASSERT_UNREACHABLE(
           "unexpected measure unit field found, even though "
@@ -507,6 +510,7 @@ static intl::FieldType GetFieldTypeForNumberField(UNumberFormatFields fieldName,
           "we don't use any user-defined patterns that "
           "would require a compact number notation");
       break;
+#  endif
 #endif
 
 #ifndef U_HIDE_DEPRECATED_API
@@ -524,29 +528,72 @@ static intl::FieldType GetFieldTypeForNumberField(UNumberFormatFields fieldName,
   return nullptr;
 }
 
-bool js::intl::NumberFormatFields::append(int32_t field, int32_t begin,
-                                          int32_t end) {
-  MOZ_ASSERT(begin >= 0);
-  MOZ_ASSERT(end >= 0);
-  MOZ_ASSERT(begin < end, "erm, aren't fields always non-empty?");
+static bool intl_FormatNumberToParts(JSContext* cx, UNumberFormat* nf, double x,
+                                     MutableHandleValue result) {
+  UErrorCode status = U_ZERO_ERROR;
 
-  FieldType type =
-      GetFieldTypeForNumberField(UNumberFormatFields(field), number_);
-  return fields_.emplaceBack(uint32_t(begin), uint32_t(end), type);
-}
+  UFieldPositionIterator* fpositer = ufieldpositer_open(&status);
+  if (U_FAILURE(status)) {
+    intl::ReportInternalError(cx);
+    return false;
+  }
 
-ArrayObject* js::intl::NumberFormatFields::toArray(JSContext* cx,
-                                                   HandleString overallResult,
-                                                   FieldType unitType) {
-  // Merge sort the fields vector.  Expand the vector to have scratch space for
-  // performing the sort.
-  size_t fieldsLen = fields_.length();
-  if (!fields_.resizeUninitialized(fieldsLen * 2)) {
-    return nullptr;
+  MOZ_ASSERT(fpositer);
+  ScopedICUObject<UFieldPositionIterator, ufieldpositer_close> toClose(
+      fpositer);
+
+  RootedString overallResult(cx, PartitionNumberPattern(cx, nf, &x, fpositer));
+  if (!overallResult) {
+    return false;
+  }
+
+  RootedArrayObject partsArray(cx, NewDenseEmptyArray(cx));
+  if (!partsArray) {
+    return false;
+  }
+
+  // First, vacuum up fields in the overall formatted string.
+
+  struct Field {
+    uint32_t begin;
+    uint32_t end;
+    FieldType type;
+
+    // Needed for vector-resizing scratch space.
+    Field() = default;
+
+    Field(uint32_t begin, uint32_t end, FieldType type)
+        : begin(begin), end(end), type(type) {}
+  };
+
+  using FieldsVector = Vector<Field, 16>;
+  FieldsVector fields(cx);
+
+  int32_t fieldInt, beginIndexInt, endIndexInt;
+  while ((fieldInt = ufieldpositer_next(fpositer, &beginIndexInt,
+                                        &endIndexInt)) >= 0) {
+    MOZ_ASSERT(beginIndexInt >= 0);
+    MOZ_ASSERT(endIndexInt >= 0);
+    MOZ_ASSERT(beginIndexInt < endIndexInt,
+               "erm, aren't fields always non-empty?");
+
+    FieldType type =
+        GetFieldTypeForNumberField(UNumberFormatFields(fieldInt), x);
+    if (!fields.emplaceBack(uint32_t(beginIndexInt), uint32_t(endIndexInt),
+                            type)) {
+      return false;
+    }
+  }
+
+  // Second, merge sort the fields vector.  Expand the vector to have scratch
+  // space for performing the sort.
+  size_t fieldsLen = fields.length();
+  if (!fields.resizeUninitialized(fieldsLen * 2)) {
+    return false;
   }
 
   MOZ_ALWAYS_TRUE(MergeSort(
-      fields_.begin(), fieldsLen, fields_.begin() + fieldsLen,
+      fields.begin(), fieldsLen, fields.begin() + fieldsLen,
       [](const Field& left, const Field& right, bool* lessOrEqual) {
         // Sort first by begin index, then to place
         // enclosing fields before nested fields.
@@ -556,13 +603,13 @@ ArrayObject* js::intl::NumberFormatFields::toArray(JSContext* cx,
       }));
 
   // Deallocate the scratch space.
-  if (!fields_.resize(fieldsLen)) {
-    return nullptr;
+  if (!fields.resize(fieldsLen)) {
+    return false;
   }
 
-  // Then iterate over the sorted field list to generate a sequence of parts
-  // (what ECMA-402 actually exposes).  A part is a maximal character sequence
-  // entirely within no field or a single most-nested field.
+  // Third, iterate over the sorted field list to generate a sequence of
+  // parts (what ECMA-402 actually exposes).  A part is a maximal character
+  // sequence entirely within no field or a single most-nested field.
   //
   // Diagrams may be helpful to illustrate how fields map to parts.  Consider
   // formatting -19,766,580,028,249.41, the US national surplus (negative
@@ -767,17 +814,12 @@ ArrayObject* js::intl::NumberFormatFields::toArray(JSContext* cx,
   RootedObject singlePart(cx);
   RootedValue propVal(cx);
 
-  RootedArrayObject partsArray(cx, NewDenseEmptyArray(cx));
-  if (!partsArray) {
-    return nullptr;
-  }
-
-  PartGenerator gen(cx, fields_, overallResult->length());
+  PartGenerator gen(cx, fields, overallResult->length());
   do {
     bool hasPart;
     Part part;
     if (!gen.nextPart(&hasPart, &part)) {
-      return nullptr;
+      return false;
     }
 
     if (!hasPart) {
@@ -791,35 +833,28 @@ ArrayObject* js::intl::NumberFormatFields::toArray(JSContext* cx,
 
     singlePart = NewBuiltinClassInstance<PlainObject>(cx);
     if (!singlePart) {
-      return nullptr;
+      return false;
     }
 
     propVal.setString(cx->names().*type);
     if (!DefineDataProperty(cx, singlePart, cx->names().type, propVal)) {
-      return nullptr;
+      return false;
     }
 
     JSLinearString* partSubstr = NewDependentString(
         cx, overallResult, lastEndIndex, endIndex - lastEndIndex);
     if (!partSubstr) {
-      return nullptr;
+      return false;
     }
 
     propVal.setString(partSubstr);
     if (!DefineDataProperty(cx, singlePart, cx->names().value, propVal)) {
-      return nullptr;
-    }
-
-    if (unitType != nullptr && type != &JSAtomState::literal) {
-      propVal.setString(cx->names().*unitType);
-      if (!DefineDataProperty(cx, singlePart, cx->names().unit, propVal)) {
-        return nullptr;
-      }
+      return false;
     }
 
     propVal.setObject(*singlePart);
     if (!DefineDataElement(cx, partsArray, partIndex, propVal)) {
-      return nullptr;
+      return false;
     }
 
     lastEndIndex = endIndex;
@@ -829,45 +864,7 @@ ArrayObject* js::intl::NumberFormatFields::toArray(JSContext* cx,
   MOZ_ASSERT(lastEndIndex == overallResult->length(),
              "result array must partition the entire string");
 
-  return partsArray;
-}
-
-static bool intl_FormatNumberToParts(JSContext* cx, UNumberFormat* nf, double x,
-                                     MutableHandleValue result) {
-  UErrorCode status = U_ZERO_ERROR;
-
-  UFieldPositionIterator* fpositer = ufieldpositer_open(&status);
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-
-  MOZ_ASSERT(fpositer);
-  ScopedICUObject<UFieldPositionIterator, ufieldpositer_close> toClose(
-      fpositer);
-
-  RootedString overallResult(cx, PartitionNumberPattern(cx, nf, &x, fpositer));
-  if (!overallResult) {
-    return false;
-  }
-
-  // Vacuum up fields in the overall formatted string.
-
-  intl::NumberFormatFields fields(cx, x);
-
-  int32_t field, beginIndex, endIndex;
-  while ((field = ufieldpositer_next(fpositer, &beginIndex, &endIndex)) >= 0) {
-    if (!fields.append(field, beginIndex, endIndex)) {
-      return false;
-    }
-  }
-
-  ArrayObject* array = fields.toArray(cx, overallResult, nullptr);
-  if (!array) {
-    return false;
-  }
-
-  result.setObject(*array);
+  result.setObject(*partsArray);
   return true;
 }
 
diff --git a/js/src/builtin/intl/NumberFormat.h b/js/src/builtin/intl/NumberFormat.h
index 5384da14d263..b6c2458ba2ce 100644
--- a/js/src/builtin/intl/NumberFormat.h
+++ b/js/src/builtin/intl/NumberFormat.h
@@ -12,15 +12,11 @@
 #include <stdint.h>
 
 #include "builtin/SelfHostingDefines.h"
-#include "gc/Barrier.h"
 #include "js/Class.h"
-#include "js/Vector.h"
 #include "vm/NativeObject.h"
-#include "vm/Runtime.h"
 
 namespace js {
 
-class ArrayObject;
 class FreeOp;
 
 class NumberFormatObject : public NativeObject {
@@ -88,40 +84,6 @@ extern MOZ_MUST_USE bool intl_numberingSystem(JSContext* cx, unsigned argc,
 extern MOZ_MUST_USE bool intl_FormatNumber(JSContext* cx, unsigned argc,
                                            Value* vp);
 
-namespace intl {
-
-using FieldType = js::ImmutablePropertyNamePtr JSAtomState::*;
-
-struct Field {
-  uint32_t begin;
-  uint32_t end;
-  FieldType type;
-
-  // Needed for vector-resizing scratch space.
-  Field() = default;
-
-  Field(uint32_t begin, uint32_t end, FieldType type)
-      : begin(begin), end(end), type(type) {}
-};
-
-class NumberFormatFields {
-  using FieldsVector = Vector<Field, 16>;
-
-  FieldsVector fields_;
-  double number_;
-
- public:
-  NumberFormatFields(JSContext* cx, double number)
-      : fields_(cx), number_(number) {}
-
-  MOZ_MUST_USE bool append(int32_t field, int32_t begin, int32_t end);
-
-  MOZ_MUST_USE ArrayObject* toArray(JSContext* cx,
-                                    JS::HandleString overallResult,
-                                    FieldType unitType);
-};
-
-}  // namespace intl
 }  // namespace js
 
 #endif /* builtin_intl_NumberFormat_h */
diff --git a/js/src/builtin/intl/RelativeTimeFormat.cpp b/js/src/builtin/intl/RelativeTimeFormat.cpp
index 86aaa83735b9..e91535fa1b96 100644
--- a/js/src/builtin/intl/RelativeTimeFormat.cpp
+++ b/js/src/builtin/intl/RelativeTimeFormat.cpp
@@ -13,19 +13,19 @@
 
 #include "builtin/intl/CommonFunctions.h"
 #include "builtin/intl/ICUStubs.h"
-#include "builtin/intl/NumberFormat.h"
 #include "builtin/intl/ScopedICUObject.h"
 #include "gc/FreeOp.h"
 #include "js/CharacterEncoding.h"
 #include "js/PropertySpec.h"
 #include "vm/GlobalObject.h"
 #include "vm/JSContext.h"
-#include "vm/StringType.h"
 
 #include "vm/NativeObject-inl.h"
 
 using namespace js;
 
+using mozilla::IsNegativeZero;
+
 using js::intl::CallICU;
 using js::intl::GetAvailableLocales;
 using js::intl::IcuLocale;
@@ -63,10 +63,6 @@ static const JSFunctionSpec relativeTimeFormat_methods[] = {
     JS_SELF_HOSTED_FN("resolvedOptions",
                       "Intl_RelativeTimeFormat_resolvedOptions", 0, 0),
     JS_SELF_HOSTED_FN("format", "Intl_RelativeTimeFormat_format", 2, 0),
-#ifndef U_HIDE_DRAFT_API
-    JS_SELF_HOSTED_FN("formatToParts", "Intl_RelativeTimeFormat_formatToParts",
-                      2, 0),
-#endif
     JS_FN(js_toSource_str, relativeTimeFormat_toSource, 0, 0), JS_FS_END};
 
 static const JSPropertySpec relativeTimeFormat_properties[] = {
@@ -261,176 +257,14 @@ enum class RelativeTimeNumeric {
   Auto,
 };
 
-static bool intl_FormatRelativeTime(JSContext* cx,
-                                    URelativeDateTimeFormatter* rtf, double t,
-                                    URelativeDateTimeUnit unit,
-                                    RelativeTimeNumeric numeric,
-                                    MutableHandleValue result) {
-  JSString* str = CallICU(
-      cx,
-      [rtf, t, unit, numeric](UChar* chars, int32_t size, UErrorCode* status) {
-        auto fmt = numeric == RelativeTimeNumeric::Auto
-                       ? ureldatefmt_format
-                       : ureldatefmt_formatNumeric;
-        return fmt(rtf, t, unit, chars, size, status);
-      });
-  if (!str) {
-    return false;
-  }
-
-  result.setString(str);
-  return true;
-}
-
-#ifndef U_HIDE_DRAFT_API
-static bool intl_FormatToPartsRelativeTime(JSContext* cx,
-                                           URelativeDateTimeFormatter* rtf,
-                                           double t, URelativeDateTimeUnit unit,
-                                           RelativeTimeNumeric numeric,
-                                           MutableHandleValue result) {
-  UErrorCode status = U_ZERO_ERROR;
-  UFormattedRelativeDateTime* formatted = ureldatefmt_openResult(&status);
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-  ScopedICUObject<UFormattedRelativeDateTime, ureldatefmt_closeResult> toClose(
-      formatted);
-
-  if (numeric == RelativeTimeNumeric::Auto) {
-    ureldatefmt_formatToResult(rtf, t, unit, formatted, &status);
-  } else {
-    ureldatefmt_formatNumericToResult(rtf, t, unit, formatted, &status);
-  }
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-
-  const UFormattedValue* formattedValue =
-      ureldatefmt_resultAsValue(formatted, &status);
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-
-  int32_t strLength;
-  const char16_t* str = ufmtval_getString(formattedValue, &strLength, &status);
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-  MOZ_ASSERT(strLength >= 0);
-
-  RootedString overallResult(cx,
-                             NewStringCopyN<CanGC>(cx, str, size_t(strLength)));
-  if (!overallResult) {
-    return false;
-  }
-
-  intl::FieldType unitType;
-  switch (unit) {
-    case UDAT_REL_UNIT_SECOND:
-      unitType = &JSAtomState::second;
-      break;
-    case UDAT_REL_UNIT_MINUTE:
-      unitType = &JSAtomState::minute;
-      break;
-    case UDAT_REL_UNIT_HOUR:
-      unitType = &JSAtomState::hour;
-      break;
-    case UDAT_REL_UNIT_DAY:
-      unitType = &JSAtomState::day;
-      break;
-    case UDAT_REL_UNIT_WEEK:
-      unitType = &JSAtomState::week;
-      break;
-    case UDAT_REL_UNIT_MONTH:
-      unitType = &JSAtomState::month;
-      break;
-    case UDAT_REL_UNIT_QUARTER:
-      unitType = &JSAtomState::quarter;
-      break;
-    case UDAT_REL_UNIT_YEAR:
-      unitType = &JSAtomState::year;
-      break;
-    default:
-      MOZ_CRASH("unexpected relative time unit");
-  }
-
-  UConstrainedFieldPosition* fpos = ucfpos_open(&status);
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-  ScopedICUObject<UConstrainedFieldPosition, ucfpos_close> toCloseFpos(fpos);
-
-  // The possible field position categories are UFIELD_CATEGORY_NUMBER and
-  // UFIELD_CATEGORY_RELATIVE_DATETIME. For the parts array we only need to
-  // iterate over the number formatted fields.
-  ucfpos_constrainCategory(fpos, UFIELD_CATEGORY_NUMBER, &status);
-  if (U_FAILURE(status)) {
-    intl::ReportInternalError(cx);
-    return false;
-  }
-
-  intl::NumberFormatFields fields(cx, t);
-
-  while (true) {
-    bool hasMore = ufmtval_nextPosition(formattedValue, fpos, &status);
-    if (U_FAILURE(status)) {
-      intl::ReportInternalError(cx);
-      return false;
-    }
-    if (!hasMore) {
-      break;
-    }
-
-    int32_t field = ucfpos_getField(fpos, &status);
-    if (U_FAILURE(status)) {
-      intl::ReportInternalError(cx);
-      return false;
-    }
-
-    int32_t beginIndex, endIndex;
-    ucfpos_getIndexes(fpos, &beginIndex, &endIndex, &status);
-    if (U_FAILURE(status)) {
-      intl::ReportInternalError(cx);
-      return false;
-    }
-
-    if (!fields.append(field, beginIndex, endIndex)) {
-      return false;
-    }
-  }
-
-  ArrayObject* array = fields.toArray(cx, overallResult, unitType);
-  if (!array) {
-    return false;
-  }
-
-  result.setObject(*array);
-  return true;
-}
-#endif
-
 bool js::intl_FormatRelativeTime(JSContext* cx, unsigned argc, Value* vp) {
   CallArgs args = CallArgsFromVp(argc, vp);
-  MOZ_ASSERT(args.length() == 5);
+  MOZ_ASSERT(args.length() == 4);
 
   Rooted<RelativeTimeFormatObject*> relativeTimeFormat(cx);
   relativeTimeFormat = &args[0].toObject().as<RelativeTimeFormatObject>();
 
-  bool formatToParts = args[4].toBoolean();
-
-  // PartitionRelativeTimePattern, step 4.
   double t = args[1].toNumber();
-  if (!mozilla::IsFinite(t)) {
-    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
-                              JSMSG_DATE_NOT_FINITE, "RelativeTimeFormat",
-                              formatToParts ? "formatToParts" : "format");
-    return false;
-  }
 
   // Obtain a cached URelativeDateTimeFormatter object.
   constexpr auto RT_FORMAT_SLOT =
@@ -453,7 +287,6 @@ bool js::intl_FormatRelativeTime(JSContext* cx, unsigned argc, Value* vp) {
       return false;
     }
 
-    // PartitionRelativeTimePattern, step 5.
     if (StringEqualsAscii(unit, "second") ||
         StringEqualsAscii(unit, "seconds")) {
       relDateTimeUnit = UDAT_REL_UNIT_SECOND;
@@ -475,16 +308,10 @@ bool js::intl_FormatRelativeTime(JSContext* cx, unsigned argc, Value* vp) {
     } else if (StringEqualsAscii(unit, "quarter") ||
                StringEqualsAscii(unit, "quarters")) {
       relDateTimeUnit = UDAT_REL_UNIT_QUARTER;
-    } else if (StringEqualsAscii(unit, "year") ||
-               StringEqualsAscii(unit, "years")) {
-      relDateTimeUnit = UDAT_REL_UNIT_YEAR;
     } else {
-      if (auto unitChars = StringToNewUTF8CharsZ(cx, *unit)) {
-        JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
-                                 JSMSG_INVALID_OPTION_VALUE, "unit",
-                                 unitChars.get());
-      }
-      return false;
+      MOZ_ASSERT(StringEqualsAscii(unit, "year") ||
+                 StringEqualsAscii(unit, "years"));
+      relDateTimeUnit = UDAT_REL_UNIT_YEAR;
     }
   }
 
@@ -503,15 +330,18 @@ bool js::intl_FormatRelativeTime(JSContext* cx, unsigned argc, Value* vp) {
     }
   }
 
-#ifndef U_HIDE_DRAFT_API
-  return formatToParts
-             ? intl_FormatToPartsRelativeTime(cx, rtf, t, relDateTimeUnit,
-                                              relDateTimeNumeric, args.rval())
-             : intl_FormatRelativeTime(cx, rtf, t, relDateTimeUnit,
-                                       relDateTimeNumeric, args.rval());
-#else
-  MOZ_ASSERT(!formatToParts);
-  return intl_FormatRelativeTime(cx, rtf, t, relDateTimeUnit,
-                                 relDateTimeNumeric, args.rval());
-#endif
+  JSString* str =
+      CallICU(cx, [rtf, t, relDateTimeUnit, relDateTimeNumeric](
+                      UChar* chars, int32_t size, UErrorCode* status) {
+        auto fmt = relDateTimeNumeric == RelativeTimeNumeric::Auto
+                       ? ureldatefmt_format
+                       : ureldatefmt_formatNumeric;
+        return fmt(rtf, t, relDateTimeUnit, chars, size, status);
+      });
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  return true;
 }
diff --git a/js/src/builtin/intl/RelativeTimeFormat.h b/js/src/builtin/intl/RelativeTimeFormat.h
index b3c71404cb30..9574c215d059 100644
--- a/js/src/builtin/intl/RelativeTimeFormat.h
+++ b/js/src/builtin/intl/RelativeTimeFormat.h
@@ -62,7 +62,7 @@ extern MOZ_MUST_USE bool intl_RelativeTimeFormat_availableLocales(
  * |numeric| should be "always" or "auto".
  *
  * Usage: formatted = intl_FormatRelativeTime(relativeTimeFormat, t,
- *                                            unit, numeric, formatToParts)
+ *                                            unit, numeric)
  */
 extern MOZ_MUST_USE bool intl_FormatRelativeTime(JSContext* cx, unsigned argc,
                                                  JS::Value* vp);
diff --git a/js/src/builtin/intl/RelativeTimeFormat.js b/js/src/builtin/intl/RelativeTimeFormat.js
index 7ce9df5fc96a..e5570930c383 100644
--- a/js/src/builtin/intl/RelativeTimeFormat.js
+++ b/js/src/builtin/intl/RelativeTimeFormat.js
@@ -201,48 +201,42 @@ function Intl_RelativeTimeFormat_format(value, unit) {
     // Step 4.
     let u = ToString(unit);
 
-    // Step 5.
-    return intl_FormatRelativeTime(relativeTimeFormat, t, u, internals.numeric,
-                                   false);
-}
-
-/**
- * Returns an Array composed of the components of a relative date formatted
- * according to the effective locale and the formatting options of this
- * RelativeTimeFormat object.
- *
- * Spec: ECMAScript 402 API, RelativeTImeFormat, 1.4.4.
- */
-function Intl_RelativeTimeFormat_formatToParts(value, unit) {
-    // Step 1.
-    let relativeTimeFormat = this;
-
-    // Step 2.
-    if (!IsObject(relativeTimeFormat) ||
-        (relativeTimeFormat = GuardToRelativeTimeFormat(relativeTimeFormat)) === null)
-    {
-        return callFunction(CallRelativeTimeFormatMethodIfWrapped, this, value, unit,
-                            "Intl_RelativeTimeFormat_formatToParts");
+    // PartitionRelativeTimePattern, step 4.
+    if (!Number_isFinite(t)) {
+        ThrowRangeError(JSMSG_DATE_NOT_FINITE, "RelativeTimeFormat");
     }
 
-    // Ensure the RelativeTimeFormat internals are resolved.
-    var internals = getRelativeTimeFormatInternals(relativeTimeFormat);
-
-    // Step 3.
-    let t = ToNumber(value);
-
-    // Step 4.
-    let u = ToString(unit);
+    // PartitionRelativeTimePattern, step 5.
+    switch (u) {
+      case "second":
+      case "seconds":
+      case "minute":
+      case "minutes":
+      case "hour":
+      case "hours":
+      case "day":
+      case "days":
+      case "week":
+      case "weeks":
+      case "month":
+      case "months":
+      case "quarter":
+      case "quarters":
+      case "year":
+      case "years":
+        break;
+      default:
+        ThrowRangeError(JSMSG_INVALID_OPTION_VALUE, "unit", u);
+    }
 
     // Step 5.
-    return intl_FormatRelativeTime(relativeTimeFormat, t, u, internals.numeric,
-                                   true);
+    return intl_FormatRelativeTime(relativeTimeFormat, t, u, internals.numeric);
 }
 
 /**
  * Returns the resolved options for a RelativeTimeFormat object.
  *
- * Spec: ECMAScript 402 API, RelativeTimeFormat, 1.4.5.
+ * Spec: ECMAScript 402 API, RelativeTimeFormat, 1.4.4.
  */
 function Intl_RelativeTimeFormat_resolvedOptions() {
     // Step 1.
diff --git a/js/src/js.msg b/js/src/js.msg
index bb0dfcaa73dc..3318d0a767d3 100644
--- a/js/src/js.msg
+++ b/js/src/js.msg
@@ -519,7 +519,7 @@ MSG_DEF(JSMSG_TESTING_SCRIPTS_ONLY, 0, JSEXN_TYPEERR, "only works on scripts")
 MSG_DEF(JSMSG_TRACELOGGER_ENABLE_FAIL, 1, JSEXN_ERR, "enabling tracelogger failed: {0}")
 
 // Intl
-MSG_DEF(JSMSG_DATE_NOT_FINITE,         2, JSEXN_RANGEERR, "date value is not finite in {0}.{1}()")
+MSG_DEF(JSMSG_DATE_NOT_FINITE,         1, JSEXN_RANGEERR, "date value is not finite in {0}.format()")
 MSG_DEF(JSMSG_INTERNAL_INTL_ERROR,     0, JSEXN_ERR, "internal error while computing Intl data")
 MSG_DEF(JSMSG_INVALID_CURRENCY_CODE,   1, JSEXN_RANGEERR, "invalid currency code in NumberFormat(): {0}")
 MSG_DEF(JSMSG_INVALID_DIGITS_VALUE,    1, JSEXN_RANGEERR, "invalid digits value: {0}")
diff --git a/js/src/tests/jstests.list b/js/src/tests/jstests.list
index 2c3c2e49ee62..162856a4f900 100644
--- a/js/src/tests/jstests.list
+++ b/js/src/tests/jstests.list
@@ -16,7 +16,6 @@ slow script test262/built-ins/decodeURIComponent/S15.1.3.2_A2.5_T1.js
 skip-if((xulRuntime.XPCOMABI.match(/aarch64/))&&(xulRuntime.OS=="WINNT")) script non262/Math/fround.js
 skip-if((xulRuntime.XPCOMABI.match(/aarch64/))&&(xulRuntime.OS=="WINNT")) script non262/Math/log2-approx.js
 
-
 ###########################################################################
 # Generated jstests.list for test262 when inline |reftest| isn't possible #
 ###########################################################################
@@ -437,6 +436,9 @@ skip script test262/annexB/built-ins/Function/createdynfn-no-line-terminator-htm
 # https://bugzilla.mozilla.org/show_bug.cgi?id=1462745
 skip script test262/annexB/language/function-code/block-decl-nested-blocks-with-fun-decl.js
 
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1473229
+skip include test262/intl402/RelativeTimeFormat/prototype/formatToParts/jstests.list
+
 # https://bugzilla.mozilla.org/show_bug.cgi?id=1508683
 skip script test262/built-ins/RegExp/prototype/multiline/cross-realm.js
 skip script test262/built-ins/RegExp/prototype/global/cross-realm.js
diff --git a/js/src/vm/CommonPropertyNames.h b/js/src/vm/CommonPropertyNames.h
index 9f160ad78264..da00e2f856b7 100644
--- a/js/src/vm/CommonPropertyNames.h
+++ b/js/src/vm/CommonPropertyNames.h
@@ -341,7 +341,6 @@
   MACRO(proto, proto, "__proto__")                                             \
   MACRO(prototype, prototype, "prototype")                                     \
   MACRO(proxy, proxy, "proxy")                                                 \
-  MACRO(quarter, quarter, "quarter")                                           \
   MACRO(raw, raw, "raw")                                                       \
   MACRO(reason, reason, "reason")                                              \
   MACRO(RegExpBuiltinExec, RegExpBuiltinExec, "RegExpBuiltinExec")             \
@@ -457,7 +456,6 @@
   MACRO(WeakSetConstructorInit, WeakSetConstructorInit,                        \
         "WeakSetConstructorInit")                                              \
   MACRO(WeakSet_add, WeakSet_add, "WeakSet_add")                               \
-  MACRO(week, week, "week")                                                    \
   MACRO(weekday, weekday, "weekday")                                           \
   MACRO(weekendEnd, weekendEnd, "weekendEnd")                                  \
   MACRO(weekendStart, weekendStart, "weekendStart")                            \