diff --git a/src/types/date-time.ts b/src/types/date-time.ts
index 0811ce8..3a6759f 100644
--- a/src/types/date-time.ts
+++ b/src/types/date-time.ts
@@ -10,10 +10,13 @@ export const types = {
 };
 
 export const fetchProcessing = (data: any) => {
-	if (data == null || data instanceof Date) {
+	if (data == null) {
 		return data;
 	}
-	return new Date(data);
+	if (!(data instanceof Date)) {
+		data = new Date(data);
+	}
+	return data.toISOString();
 };
 
 export const nativeFactTypes = {
diff --git a/src/types/date.ts b/src/types/date.ts
index 60c5757..95c04f5 100644
--- a/src/types/date.ts
+++ b/src/types/date.ts
@@ -10,10 +10,13 @@ export const types = {
 };
 
 export const fetchProcessing = (data: any) => {
-	if (data == null || data instanceof Date) {
+	if (data == null) {
 		return data;
 	}
-	return new Date(data);
+	if (!(data instanceof Date)) {
+		data = new Date(data);
+	}
+	return data.toISOString();
 };
 
 export const nativeFactTypes = {
diff --git a/src/types/time.ts b/src/types/time.ts
index 3b54873..1dba8fc 100644
--- a/src/types/time.ts
+++ b/src/types/time.ts
@@ -12,7 +12,7 @@ export const types = {
 export const fetchProcessing = (data: any) => {
 	if (data != null) {
 		// We append the date of the epoch so that we can parse this as a valid date.
-		return new Date('Thu, 01 Jan 1970 ' + data);
+		return new Date('Thu, 01 Jan 1970 ' + data).toISOString();
 	}
 	return data;
 };
diff --git a/test/Date Time.js b/test/Date Time.js
index 67d6e6f..c46ead1 100644
--- a/test/Date Time.js	
+++ b/test/Date Time.js	
@@ -3,9 +3,9 @@ import * as helpers from './helpers';
 helpers.describe('Date Time', function (test) {
 	const now = new Date();
 	describe('fetchProcessing', function () {
-		test.fetch(now, now);
-		test.fetch(now.toString(), now);
-		test.fetch(now.getTime(), now);
+		test.fetch(now, now.toISOString());
+		test.fetch(now.toString(), new Date(now.toString()).toISOString());
+		test.fetch(now.getTime(), new Date(now.getTime()).toISOString());
 		test.fetch(null, null);
 	});
 
diff --git a/test/Date.js b/test/Date.js
index ec2ae1d..638fbae 100644
--- a/test/Date.js
+++ b/test/Date.js
@@ -3,9 +3,9 @@ import * as helpers from './helpers';
 helpers.describe('Date', function (test) {
 	const now = new Date();
 	describe('fetchProcessing', function () {
-		test.fetch(now, now);
-		test.fetch(now.toString(), now);
-		test.fetch(now.getTime(), now);
+		test.fetch(now, now.toISOString());
+		test.fetch(now.toString(), new Date(now.toString()).toISOString());
+		test.fetch(now.getTime(), new Date(now.getTime()).toISOString());
 		test.fetch(null, null);
 	});
 
diff --git a/test/Time.js b/test/Time.js
index 7092344..623b8bf 100644
--- a/test/Time.js
+++ b/test/Time.js
@@ -6,7 +6,10 @@ helpers.describe('Time', function (test) {
 	now.setMonth(0);
 	now.setDate(1);
 	describe('fetchProcessing', function () {
-		test.fetch(now.toTimeString(), now);
+		test.fetch(
+			now.toTimeString(),
+			new Date('Thu, 01 Jan 1970 ' + now.toTimeString()).toISOString(),
+		);
 		test.fetch(null, null);
 	});