diff --git a/Userland/Libraries/LibJS/Runtime/Intl/DateTimeFormat.cpp b/Userland/Libraries/LibJS/Runtime/Intl/DateTimeFormat.cpp
index 63bd48aa86..852a055dfb 100644
--- a/Userland/Libraries/LibJS/Runtime/Intl/DateTimeFormat.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Intl/DateTimeFormat.cpp
@@ -1492,15 +1492,14 @@ ThrowCompletionOr<Array*> format_date_time_range_to_parts(GlobalObject& global_o
 }
 
 // 11.1.14 ToLocalTime ( t, calendar, timeZone ), https://tc39.es/ecma402/#sec-tolocaltime
-ThrowCompletionOr<LocalTime> to_local_time(GlobalObject& global_object, double time, StringView calendar, [[maybe_unused]] StringView time_zone)
+ThrowCompletionOr<LocalTime> to_local_time(GlobalObject& global_object, double time, StringView calendar, StringView time_zone)
 {
     // 1. Assert: Type(t) is Number.
 
     // 2. If calendar is "gregory", then
     if (calendar == "gregory"sv) {
         // a. Let timeZoneOffset be the value calculated according to LocalTZA(t, true) where the local time zone is replaced with timezone timeZone.
-        // FIXME: Implement LocalTZA when timezones other than UTC are supported.
-        double time_zone_offset = 0;
+        double time_zone_offset = local_tza(time, true, time_zone);
 
         // b. Let tz be the time value t + timeZoneOffset.
         double zoned_time = time + time_zone_offset;
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.format.js b/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.format.js
index da599067b1..06dddb4dd0 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.format.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.format.js
@@ -389,13 +389,10 @@ describe("timeZoneName", () => {
         { timeZone: "UTC", timeZoneName: "longOffset", en0: "12/7/2021, 5:40 PM GMT", en1: "1/23/1989, 7:08 AM GMT", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م غرينتش", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص غرينتش" },
         { timeZone: "UTC", timeZoneName: "shortGeneric", en0: "12/7/2021, 5:40 PM GMT", en1: "1/23/1989, 7:08 AM GMT", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م غرينتش", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص غرينتش" },
         { timeZone: "UTC", timeZoneName: "longGeneric", en0: "12/7/2021, 5:40 PM GMT", en1: "1/23/1989, 7:08 AM GMT", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م غرينتش", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص غرينتش" },
-
-        // FIXME: The time stamps on the below cases are incorrect as they do not adjust the time based on the GMT offset.
-        //        Update these once the LocalTZA AO is implemented and ToLocalTime uses it.
-        { timeZone: "America/New_York", timeZoneName: "shortOffset", en0: "12/7/2021, 5:40 PM GMT-5", en1: "1/23/1989, 7:08 AM GMT-5", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م غرينتش-٥", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص غرينتش-٥" },
-        { timeZone: "America/New_York", timeZoneName: "longOffset", en0: "12/7/2021, 5:40 PM GMT-05:00", en1: "1/23/1989, 7:08 AM GMT-05:00", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م غرينتش-٠٥:٠٠", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص غرينتش-٠٥:٠٠" },
-        { timeZone: "America/New_York", timeZoneName: "shortGeneric", en0: "12/7/2021, 5:40 PM ET", en1: "1/23/1989, 7:08 AM ET", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م غرينتش-٥", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص غرينتش-٥" },
-        { timeZone: "America/New_York", timeZoneName: "longGeneric", en0: "12/7/2021, 5:40 PM Eastern Time", en1: "1/23/1989, 7:08 AM Eastern Time", ar0: "٧‏/١٢‏/٢٠٢١, ٥:٤٠ م التوقيت الشرقي لأمريكا الشمالية", ar1: "٢٣‏/١‏/١٩٨٩, ٧:٠٨ ص التوقيت الشرقي لأمريكا الشمالية" },
+        { timeZone: "America/New_York", timeZoneName: "shortOffset", en0: "12/7/2021, 12:40 PM GMT-5", en1: "1/23/1989, 2:08 AM GMT-5", ar0: "٧‏/١٢‏/٢٠٢١, ١٢:٤٠ م غرينتش-٥", ar1: "٢٣‏/١‏/١٩٨٩, ٢:٠٨ ص غرينتش-٥" },
+        { timeZone: "America/New_York", timeZoneName: "longOffset", en0: "12/7/2021, 12:40 PM GMT-05:00", en1: "1/23/1989, 2:08 AM GMT-05:00", ar0: "٧‏/١٢‏/٢٠٢١, ١٢:٤٠ م غرينتش-٠٥:٠٠", ar1: "٢٣‏/١‏/١٩٨٩, ٢:٠٨ ص غرينتش-٠٥:٠٠" },
+        { timeZone: "America/New_York", timeZoneName: "shortGeneric", en0: "12/7/2021, 12:40 PM ET", en1: "1/23/1989, 2:08 AM ET", ar0: "٧‏/١٢‏/٢٠٢١, ١٢:٤٠ م غرينتش-٥", ar1: "٢٣‏/١‏/١٩٨٩, ٢:٠٨ ص غرينتش-٥" },
+        { timeZone: "America/New_York", timeZoneName: "longGeneric", en0: "12/7/2021, 12:40 PM Eastern Time", en1: "1/23/1989, 2:08 AM Eastern Time", ar0: "٧‏/١٢‏/٢٠٢١, ١٢:٤٠ م التوقيت الشرقي لأمريكا الشمالية", ar1: "٢٣‏/١‏/١٩٨٩, ٢:٠٨ ص التوقيت الشرقي لأمريكا الشمالية" },
     ];
 
     test("all", () => {
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.formatRangeToParts.js b/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.formatRangeToParts.js
index 86406a826c..c0d18d2341 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.formatRangeToParts.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.formatRangeToParts.js
@@ -347,7 +347,7 @@ describe("timeStyle", () => {
     // FIXME: These results should include the date, even though it isn't requested, because the start/end dates
     //        are more than just hours apart. See the FIXME in PartitionDateTimeRangePattern.
     test("full", () => {
-        const en = new Intl.DateTimeFormat("en", { timeStyle: "full" });
+        const en = new Intl.DateTimeFormat("en", { timeStyle: "full", timeZone: "UTC" });
         expect(en.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
@@ -370,7 +370,7 @@ describe("timeStyle", () => {
             { type: "timeZoneName", value: "Coordinated Universal Time", source: "endRange" },
         ]);
 
-        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "full" });
+        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "full", timeZone: "UTC" });
         expect(ja.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: "時", source: "startRange" },
@@ -391,7 +391,7 @@ describe("timeStyle", () => {
     });
 
     test("long", () => {
-        const en = new Intl.DateTimeFormat("en", { timeStyle: "long" });
+        const en = new Intl.DateTimeFormat("en", { timeStyle: "long", timeZone: "UTC" });
         expect(en.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
@@ -414,7 +414,7 @@ describe("timeStyle", () => {
             { type: "timeZoneName", value: "UTC", source: "endRange" },
         ]);
 
-        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "long" });
+        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "long", timeZone: "UTC" });
         expect(ja.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
@@ -435,7 +435,7 @@ describe("timeStyle", () => {
     });
 
     test("medium", () => {
-        const en = new Intl.DateTimeFormat("en", { timeStyle: "medium" });
+        const en = new Intl.DateTimeFormat("en", { timeStyle: "medium", timeZone: "UTC" });
         expect(en.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
@@ -454,7 +454,7 @@ describe("timeStyle", () => {
             { type: "dayPeriod", value: "PM", source: "endRange" },
         ]);
 
-        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "medium" });
+        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "medium", timeZone: "UTC" });
         expect(ja.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
@@ -471,7 +471,7 @@ describe("timeStyle", () => {
     });
 
     test("short", () => {
-        const en = new Intl.DateTimeFormat("en", { timeStyle: "short" });
+        const en = new Intl.DateTimeFormat("en", { timeStyle: "short", timeZone: "UTC" });
         expect(en.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
@@ -486,7 +486,7 @@ describe("timeStyle", () => {
             { type: "dayPeriod", value: "PM", source: "endRange" },
         ]);
 
-        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "short" });
+        const ja = new Intl.DateTimeFormat("ja", { timeStyle: "short", timeZone: "UTC" });
         expect(ja.formatRangeToParts(d0, d1)).toEqual([
             { type: "hour", value: "7", source: "startRange" },
             { type: "literal", value: ":", source: "startRange" },
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.resolvedOptions.js b/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.resolvedOptions.js
index dbcd9e5f80..01c6640bf5 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.resolvedOptions.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/Intl/DateTimeFormat/DateTimeFormat.prototype.resolvedOptions.js
@@ -86,8 +86,8 @@ describe("correct behavior", () => {
     });
 
     test("style", () => {
-        const en = new Intl.DateTimeFormat("en");
-        expect(en.resolvedOptions().timeZone).toBe("UTC");
+        const en = new Intl.DateTimeFormat("en", { timeZone: "EST" });
+        expect(en.resolvedOptions().timeZone).toBe("EST");
 
         const el = new Intl.DateTimeFormat("el", { timeZone: "UTC" });
         expect(el.resolvedOptions().timeZone).toBe("UTC");