diff --git a/src/schematype.ts b/src/schematype.ts
index 5983af7..0ba0b6d 100644
--- a/src/schematype.ts
+++ b/src/schematype.ts
@@ -64,7 +64,7 @@ class SchemaType<T> {
     const default_ = this.options.default;
 
     if (typeof default_ === 'function') {
-      this.default = default_ as unknown as () => T;
+      this.default = default_ as () => T;
     } else {
       this.default = () => default_;
     }
diff --git a/src/types/array.ts b/src/types/array.ts
index 493dbce..dd27c7f 100644
--- a/src/types/array.ts
+++ b/src/types/array.ts
@@ -34,10 +34,10 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @return {Array}
    */
   cast(value_: Exclude<unknown, null | undefined>, data?: unknown): I[];
-  cast(value_?: unknown, data?: unknown): I[] | null | undefined;
-  cast(value_?: unknown, data?: unknown): I[] | null | undefined {
+  cast(value_?: unknown, data?: unknown): I[] | undefined;
+  cast(value_?: unknown, data?: unknown): I[] | undefined {
     value_ = super.cast(value_, data);
-    if (value_ == null) return value_ as null | undefined;
+    if (value_ == null) return value_ as undefined;
 
     const value = isArray(value_) ? value_ : value_ = [value_];
     if (!value.length) return value;
diff --git a/src/types/buffer.ts b/src/types/buffer.ts
index 7cb1da7..f5927ff 100644
--- a/src/types/buffer.ts
+++ b/src/types/buffer.ts
@@ -28,11 +28,11 @@ class SchemaTypeBuffer extends SchemaType<Buffer> {
    * @return {Buffer}
    */
   cast(value_: WithImplicitCoercion<Uint8Array | ReadonlyArray<number> | string>, data?: unknown): Buffer;
-  cast(value_?: unknown, data?: unknown): Buffer | null | undefined;
-  cast(value_?: unknown, data?: unknown): Buffer | null | undefined {
+  cast(value_?: unknown, data?: unknown): Buffer | undefined;
+  cast(value_?: unknown, data?: unknown): Buffer | undefined {
     const value = super.cast(value_, data);
 
-    if (value == null || Buffer.isBuffer(value)) return value as Buffer | null | undefined;
+    if (value == null || Buffer.isBuffer(value)) return value as Buffer | undefined;
     if (typeof value === 'string') return Buffer.from(value, this.options.encoding);
     if (Array.isArray(value)) return Buffer.from(value);
   }
diff --git a/src/types/date.ts b/src/types/date.ts
index 636e29b..398d09e 100644
--- a/src/types/date.ts
+++ b/src/types/date.ts
@@ -13,11 +13,11 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @return {Date | null | undefined}
    */
   cast(value_: Date | number | string): Date;
-  cast(value_?: unknown): Date | null | undefined;
-  cast(value_?: unknown): Date | null | undefined {
+  cast(value_?: unknown): Date | undefined;
+  cast(value_?: unknown): Date | undefined {
     const value = super.cast(value_, null);
 
-    if (value == null || value instanceof Date) return value as Date | null | undefined;
+    if (value == null || value instanceof Date) return value as Date | undefined;
 
     return new Date(value as any);
   }
@@ -63,7 +63,7 @@ class SchemaTypeDate extends SchemaType<Date> {
    */
   compare(a?: Date, b?: Date): number {
     if (a) {
-      return b ? (a as unknown as number) - (b as unknown as number) : 1;
+      return b ? a.getTime() - b.getTime() : 1;
     }
 
     return b ? -1 : 0;
diff --git a/src/types/number.ts b/src/types/number.ts
index fdae9c8..6b0a072 100644
--- a/src/types/number.ts
+++ b/src/types/number.ts
@@ -14,11 +14,11 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @return {Number}
    */
   cast(value_: Exclude<unknown, undefined | null>, data?: unknown): number;
-  cast(value_?: unknown, data?: unknown): number | null | undefined;
-  cast(value_?: unknown, data?: unknown): number | null | undefined {
+  cast(value_?: unknown, data?: unknown): number | undefined;
+  cast(value_?: unknown, data?: unknown): number | undefined {
     const value = super.cast(value_, data);
 
-    if (value == null || typeof value === 'number') return value as number | null | undefined;
+    if (value == null || typeof value === 'number') return value as number | undefined;
 
     return +value;
   }
diff --git a/src/types/string.ts b/src/types/string.ts
index f0c67bc..03d9be1 100644
--- a/src/types/string.ts
+++ b/src/types/string.ts
@@ -14,11 +14,11 @@ class SchemaTypeString extends SchemaType<string> {
    * @return {String}
    */
   cast(value_: { toString(): string }, data?: unknown): string;
-  cast(value_?: unknown, data?: unknown): string | null | undefined;
-  cast(value_?: unknown, data?: unknown): string | null | undefined {
+  cast(value_?: unknown, data?: unknown): string | undefined;
+  cast(value_?: unknown, data?: unknown): string | undefined {
     const value = super.cast(value_, data);
 
-    if (value == null || typeof value === 'string') return value as string | null | undefined;
+    if (value == null || typeof value === 'string') return value as string | undefined;
     if (typeof value.toString === 'function') return value.toString();
   }