diff --git a/packages/quicktype-core/src/language/CPlusPlus/CPlusPlusRenderer.ts b/packages/quicktype-core/src/language/CPlusPlus/CPlusPlusRenderer.ts
index ab8fce746e..5f51b96a09 100644
--- a/packages/quicktype-core/src/language/CPlusPlus/CPlusPlusRenderer.ts
+++ b/packages/quicktype-core/src/language/CPlusPlus/CPlusPlusRenderer.ts
@@ -1542,7 +1542,7 @@ export class CPlusPlusRenderer extends ConvenienceRenderer {
                             key,
                             ") != j.end() && !std::regex_match(j.at(",
                             key,
-                            ').get<std::string>(), std::regex("^[0-9]{4}-[0-9]{2}-[0-9]{2}T.*$"))) throw std::runtime_error("Expected date-time");',
+                            ').get<std::string>(), std::regex("^(?:(?:[0-9]{4}-(?:0[13578]|1[02])-(?:0[1-9]|[12][0-9]|3[01]))|(?:[0-9]{4}-(?:0[469]|11)-(?:0[1-9]|[12][0-9]|30))|(?:[0-9]{4}-02-(?:0[1-9]|1[0-9]|2[0-8]))|(?:(?:[0-9]{2}(?:0[48]|[2468][048]|[13579][26])|(?:[02468][048]|[13579][26])00)-02-29))[Tt](?:[01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9](?:[.][0-9]+)?(?:[Zz]|[+-](?:[01][0-9]|2[0-3]):[0-5][0-9])?$"))) throw std::runtime_error("Expected date-time");',
                         );
                     }
 
diff --git a/packages/quicktype-core/src/language/Objective-C/ObjectiveCRenderer.ts b/packages/quicktype-core/src/language/Objective-C/ObjectiveCRenderer.ts
index eb970fda54..8d19dd50f5 100644
--- a/packages/quicktype-core/src/language/Objective-C/ObjectiveCRenderer.ts
+++ b/packages/quicktype-core/src/language/Objective-C/ObjectiveCRenderer.ts
@@ -936,7 +936,10 @@ export class ObjectiveCRenderer extends ConvenienceRenderer {
                                 }
                                 if (property.type.kind === "date-time") {
                                     this.emitLine(
-                                        `if (dict[@"${objectiveCStringEscape(jsonName)}"] && [dict[@"${objectiveCStringEscape(jsonName)}"] rangeOfString:@"^[0-9]{4}-[0-9]{2}-[0-9]{2}T" options:NSRegularExpressionSearch].location == NSNotFound) return nil;`,
+                                        `if (dict[@"${objectiveCStringEscape(jsonName)}"] && [dict[@"${objectiveCStringEscape(jsonName)}"] rangeOfString:@"^[0-9]{4}-[0-9]{2}-[0-9]{2}[Tt](?:[01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9](?:\\\\.[0-9]+)?(?:[Zz]|[+-](?:[01][0-9]|2[0-3]):[0-5][0-9])?$" options:NSRegularExpressionSearch].location == NSNotFound) return nil;`,
+                                    );
+                                    this.emitLine(
+                                        `if (dict[@"${objectiveCStringEscape(jsonName)}"] && ![[[[NSISO8601DateFormatter new] stringFromDate:[[NSISO8601DateFormatter new] dateFromString:[[dict[@"${objectiveCStringEscape(jsonName)}"] substringToIndex:10] stringByAppendingString:@"T00:00:00Z"]]] substringToIndex:10] isEqualToString:[dict[@"${objectiveCStringEscape(jsonName)}"] substringToIndex:10]]) return nil;`,
                                     );
                                 }
                                 if (
diff --git a/packages/quicktype-core/src/language/Php/PhpRenderer.ts b/packages/quicktype-core/src/language/Php/PhpRenderer.ts
index f468f82635..4d3dde8097 100644
--- a/packages/quicktype-core/src/language/Php/PhpRenderer.ts
+++ b/packages/quicktype-core/src/language/Php/PhpRenderer.ts
@@ -798,6 +798,14 @@ export class PhpRenderer extends ConvenienceRenderer {
             (transformedStringType) => {
                 if (transformedStringType.kind === "date-time") {
                     this.emitLine("$tmp = ", "new DateTime(", args, ");");
+                    this.emitLine("$errors = DateTime::getLastErrors();");
+                    this.emitBlock(
+                        "if ($errors && ($errors['warning_count'] || $errors['error_count']))",
+                        () =>
+                            this.emitLine(
+                                "throw new Exception('Invalid date-time');",
+                            ),
+                    );
                     this.transformDateTime(className, "", ["$tmp"]);
                     this.emitLine("return $tmp;");
                     return;
diff --git a/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts b/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts
index 6d22b46ed2..4963e2aaff 100644
--- a/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts
+++ b/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts
@@ -749,15 +749,19 @@ export class SwiftRenderer extends ConvenienceRenderer {
                 this.emitBlock(
                     "if #available(iOS 10.0, OSX 10.12, tvOS 10.0, watchOS 3.0, *)",
                     () => {
-                        this.emitLine(
-                            "decoder.dateDecodingStrategy = .iso8601",
-                        );
+                        this.emitMultiline(`decoder.dateDecodingStrategy = .custom { decoder in
+    let dateStr = try decoder.singleValueContainer().decode(String.self).uppercased()
+    let dateData = try JSONEncoder().encode(dateStr)
+    let dateDecoder = JSONDecoder()
+    dateDecoder.dateDecodingStrategy = .iso8601
+    return try dateDecoder.decode(Date.self, from: dateData)
+}`);
                     },
                 );
             } else {
                 this.emitMultiline(`decoder.dateDecodingStrategy = .custom({ (decoder) -> Date in
 	let container = try decoder.singleValueContainer()
-	let dateStr = try container.decode(String.self)
+	let dateStr = try container.decode(String.self).uppercased()
 
 	let formatter = DateFormatter()
 	formatter.calendar = Calendar(identifier: .iso8601)
diff --git a/test/inputs/schema/date-time.12.fail.date-time.json b/test/inputs/schema/date-time.12.fail.date-time.json
new file mode 100644
index 0000000000..fe33668ae1
--- /dev/null
+++ b/test/inputs/schema/date-time.12.fail.date-time.json
@@ -0,0 +1,7 @@
+{
+  "date": "1985-04-12",
+  "time": "23:20:50.52Z",
+  "date-time": "2023-00-15T12:00:00Z",
+  "union-array": ["1985-04-12", "23:20:50.52Z"],
+  "complex-union-array": ["2018-08-13T21:31:01+00:10", "foo", 123]
+}