LibJS: Add Date.parse formats for the output of Date.prototype.to*String

We currently cannot parse the output of `toString` and `toUTCString`.
While the spec does not require such support, test262 expects it, and
all major engines support it.

Userland/Libraries/LibJS/CMakeLists.txt

@@ -267,7 +267,7 @@ set(SOURCES
 )
 
 serenity_lib(LibJS js)
-target_link_libraries(LibJS PRIVATE LibCore LibCrypto LibFileSystem LibRegex LibSyntax LibLocale LibUnicode LibJIT)
+target_link_libraries(LibJS PRIVATE LibCore LibCrypto LibFileSystem LibRegex LibSyntax LibLocale LibUnicode LibTimeZone LibJIT)
 if("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86_64")
     target_link_libraries(LibJS PRIVATE LibX86)
 endif()

Userland/Libraries/LibJS/Runtime/DateConstructor.cpp

@@ -159,12 +159,14 @@ static double parse_date_string(DeprecatedString const& date_string)
     //        Both Chrome and Firefox seem to support "4/17/2019 11:08 PM +0000" with most parts
     //        being optional, however this is not clearly documented anywhere.
     static constexpr auto extra_formats = AK::Array {
-        "%a %b %e %T %z %Y"sv, // "Wed Apr 17 23:08:53 +0000 2019"
-        "%m/%e/%Y"sv,          // "4/17/2019"
-        "%m/%e/%Y %R %z"sv,    // "12/05/2022 10:00 -0800"
-        "%Y/%m/%e %R"sv,       // "2014/11/14 13:05"
-        "%Y-%m-%e %R"sv,       // "2014-11-14 13:05"
-        "%B %e, %Y %T"sv,      //  "June 5, 2023 17:00:00"
+        "%a %b %d %Y %T GMT%z (%+)"sv, // "Tue Nov 07 2023 10:05:55 GMT-0500 (Eastern Standard Time)"
+        "%a, %d %b %Y %T %Z"sv,        // "Tue, 07 Nov 2023 15:05:55 GMT"
+        "%a %b %e %T %z %Y"sv,         // "Wed Apr 17 23:08:53 +0000 2019"
+        "%m/%e/%Y"sv,                  // "4/17/2019"
+        "%m/%e/%Y %R %z"sv,            // "12/05/2022 10:00 -0800"
+        "%Y/%m/%e %R"sv,               // "2014/11/14 13:05"
+        "%Y-%m-%e %R"sv,               // "2014-11-14 13:05"
+        "%B %e, %Y %T"sv,              //  "June 5, 2023 17:00:00"
     };
 
     for (auto const& format : extra_formats) {

Userland/Libraries/LibJS/Tests/builtins/Date/Date.parse.js

@@ -119,3 +119,67 @@ test("Month dd, yy hh:mm:ss extension", () => {
     expectStringToGiveDate("May 30, 2023 17:00:00", 2023, 5, 30, 17, 0, 0);
     expectStringToGiveDate("June 5, 2023 17:00:00", 2023, 6, 5, 17, 0, 0);
 });
+
+test("Date.prototype.toString extension", () => {
+    function expectStringToGiveDate(input, fullYear, month, dayInMonth, hours) {
+        const date = new Date(Date.parse(input));
+        expect(date.getFullYear()).toBe(fullYear);
+        expect(date.getMonth() + 1).toBe(month);
+        expect(date.getDate()).toBe(dayInMonth);
+        expect(date.getHours()).toBe(hours);
+    }
+
+    const time1 = "Tue Nov 07 2023 10:00:00 GMT-0500 (Eastern Standard Time)";
+    const time2 = "Tue Nov 07 2023 10:00:00 GMT+0100 (Central European Standard Time)";
+    const time3 = "Tue Nov 07 2023 10:00:00 GMT+0800 (Australian Western Standard Time)";
+
+    const originalTimeZone = setTimeZone("UTC");
+    expectStringToGiveDate(time1, 2023, 11, 7, 15);
+    expectStringToGiveDate(time2, 2023, 11, 7, 9);
+    expectStringToGiveDate(time3, 2023, 11, 7, 2);
+
+    setTimeZone("America/New_York");
+    expectStringToGiveDate(time1, 2023, 11, 7, 10);
+    expectStringToGiveDate(time2, 2023, 11, 7, 4);
+    expectStringToGiveDate(time3, 2023, 11, 6, 21);
+
+    setTimeZone("Australia/Perth");
+    expectStringToGiveDate(time1, 2023, 11, 7, 23);
+    expectStringToGiveDate(time2, 2023, 11, 7, 17);
+    expectStringToGiveDate(time3, 2023, 11, 7, 10);
+
+    // FIXME: Create a scoped time zone helper when bytecode supports the `using` declaration.
+    setTimeZone(originalTimeZone);
+});
+
+test("Date.prototype.toUTCString extension", () => {
+    function expectStringToGiveDate(input, fullYear, month, dayInMonth, hours) {
+        const date = new Date(Date.parse(input));
+        expect(date.getFullYear()).toBe(fullYear);
+        expect(date.getMonth() + 1).toBe(month);
+        expect(date.getDate()).toBe(dayInMonth);
+        expect(date.getHours()).toBe(hours);
+    }
+
+    const time = "Tue, 07 Nov 2023 15:00:00 GMT";
+
+    const originalTimeZone = setTimeZone("UTC");
+    expectStringToGiveDate(time, 2023, 11, 7, 15);
+
+    setTimeZone("America/New_York");
+    expectStringToGiveDate(time, 2023, 11, 7, 10);
+
+    setTimeZone("Australia/Perth");
+    expectStringToGiveDate(time, 2023, 11, 7, 23);
+
+    // FIXME: Create a scoped time zone helper when bytecode supports the `using` declaration.
+    setTimeZone(originalTimeZone);
+});
+
+test("Round trip Date.prototype.to*String", () => {
+    const epoch = new Date(0);
+
+    expect(Date.parse(epoch.toString())).toBe(epoch.valueOf());
+    expect(Date.parse(epoch.toISOString())).toBe(epoch.valueOf());
+    expect(Date.parse(epoch.toUTCString())).toBe(epoch.valueOf());
+});