diff --git a/packages/quicktype-core/src/language/Java/DateTimeProvider.ts b/packages/quicktype-core/src/language/Java/DateTimeProvider.ts
index 2535fcdfac..6298f885a3 100644
--- a/packages/quicktype-core/src/language/Java/DateTimeProvider.ts
+++ b/packages/quicktype-core/src/language/Java/DateTimeProvider.ts
@@ -6,6 +6,7 @@ export abstract class JavaDateTimeProvider {
     public constructor(
         protected readonly _renderer: JavaRenderer,
         protected readonly _className: string,
+        protected readonly _useStrictDateTime = false,
     ) {}
 
     public abstract keywords: string[];
@@ -105,15 +106,20 @@ export class Java8DateTimeProvider extends JavaDateTimeProvider {
                     ".appendOptional(DateTimeFormatter.ISO_INSTANT)",
                 );
                 this._renderer.emitLine(
-                    '.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SX"))',
+                    '.appendOptional(DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SX"))',
                 );
                 this._renderer.emitLine(
-                    '.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ssX"))',
+                    '.appendOptional(DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ssX"))',
                 );
                 this._renderer.emitLine(
-                    '.appendOptional(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"))',
+                    '.appendOptional(DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss"))',
                 );
                 this._renderer.emitLine(".toFormatter()");
+                if (this._useStrictDateTime) {
+                    this._renderer.emitLine(
+                        ".withResolverStyle(java.time.format.ResolverStyle.STRICT)",
+                    );
+                }
                 this._renderer.emitLine(".withZone(ZoneOffset.UTC);");
             }),
         );
diff --git a/packages/quicktype-core/src/language/Java/JavaRenderer.ts b/packages/quicktype-core/src/language/Java/JavaRenderer.ts
index 3817dcc9f0..a18ad85563 100644
--- a/packages/quicktype-core/src/language/Java/JavaRenderer.ts
+++ b/packages/quicktype-core/src/language/Java/JavaRenderer.ts
@@ -78,6 +78,9 @@ export class JavaRenderer extends ConvenienceRenderer {
                 this._dateTimeProvider = new Java8DateTimeProvider(
                     this,
                     this._converterClassname,
+                    [...renderContext.typeGraph.allTypesUnordered()].some(
+                        (t) => t.kind === "date-time",
+                    ),
                 );
                 break;
         }
diff --git a/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts b/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts
index 4963e2aaff..7130022215 100644
--- a/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts
+++ b/packages/quicktype-core/src/language/Swift/SwiftRenderer.ts
@@ -48,6 +48,8 @@ export class SwiftRenderer extends ConvenienceRenderer {
 
     private _needNull = false;
 
+    private _haveDateTime = false;
+
     public constructor(
         targetLanguage: TargetLanguage,
         renderContext: RenderContext,
@@ -215,6 +217,7 @@ export class SwiftRenderer extends ConvenienceRenderer {
             },
             (transformedStringType) => {
                 if (transformedStringType.kind === "date-time") {
+                    this._haveDateTime = true;
                     return "Date";
                 }
                 if (transformedStringType.kind === "uuid") return "UUID";
@@ -743,6 +746,23 @@ export class SwiftRenderer extends ConvenienceRenderer {
     }
 
     private emitNewEncoderDecoder(): void {
+        if (this._haveDateTime) {
+            this.emitMultiline(`private func isValidDate(_ value: String) -> Bool {
+    let formatter = DateFormatter()
+    formatter.locale = Locale(identifier: "en_US_POSIX")
+    formatter.timeZone = TimeZone(secondsFromGMT: 0)
+    formatter.dateFormat = "u-MM-dd"
+    formatter.isLenient = false
+    return formatter.date(from: String(value.prefix(10))) != nil
+}`);
+            this.ensureBlankLine();
+        }
+        const dateValidation = this._haveDateTime
+            ? `
+    guard isValidDate(dateStr) else {
+        throw DecodingError.dataCorrupted(.init(codingPath: decoder.codingPath, debugDescription: "Invalid date"))
+    }`
+            : "";
         this.emitBlock("func newJSONDecoder() -> JSONDecoder", () => {
             this.emitLine("let decoder = JSONDecoder()");
             if (!this._options.linux) {
@@ -750,7 +770,7 @@ export class SwiftRenderer extends ConvenienceRenderer {
                     "if #available(iOS 10.0, OSX 10.12, tvOS 10.0, watchOS 3.0, *)",
                     () => {
                         this.emitMultiline(`decoder.dateDecodingStrategy = .custom { decoder in
-    let dateStr = try decoder.singleValueContainer().decode(String.self).uppercased()
+    let dateStr = try decoder.singleValueContainer().decode(String.self).uppercased()${dateValidation}
     let dateData = try JSONEncoder().encode(dateStr)
     let dateDecoder = JSONDecoder()
     dateDecoder.dateDecodingStrategy = .iso8601
@@ -761,7 +781,7 @@ export class SwiftRenderer extends ConvenienceRenderer {
             } else {
                 this.emitMultiline(`decoder.dateDecodingStrategy = .custom({ (decoder) -> Date in
 	let container = try decoder.singleValueContainer()
-	let dateStr = try container.decode(String.self).uppercased()
+	let dateStr = try container.decode(String.self).uppercased()${dateValidation}
 
 	let formatter = DateFormatter()
 	formatter.calendar = Calendar(identifier: .iso8601)
diff --git a/test/inputs/schema/date-time.11.fail.date-time.json b/test/inputs/schema/date-time.11.fail.date-time.json
new file mode 100644
index 0000000000..34582b9df5
--- /dev/null
+++ b/test/inputs/schema/date-time.11.fail.date-time.json
@@ -0,0 +1,7 @@
+{
+  "date": "1985-04-12",
+  "time": "23:20:50.52Z",
+  "date-time": "1900-02-29T12:00:00Z",
+  "union-array": ["1985-04-12", "23:20:50.52Z"],
+  "complex-union-array": ["2018-08-13T21:31:01+00:10", "foo", 123]
+}
diff --git a/test/inputs/schema/date-time.9.fail.date-time.json b/test/inputs/schema/date-time.9.fail.date-time.json
new file mode 100644
index 0000000000..9c07dc2bbb
--- /dev/null
+++ b/test/inputs/schema/date-time.9.fail.date-time.json
@@ -0,0 +1,7 @@
+{
+  "date": "1985-04-12",
+  "time": "23:20:50.52Z",
+  "date-time": "2023-02-29T12:00:00Z",
+  "union-array": ["1985-04-12", "23:20:50.52Z"],
+  "complex-union-array": ["2018-08-13T21:31:01+00:10", "foo", 123]
+}