diff --git a/specs/PKPass.spec.cjs b/specs/PKPass.spec.cjs
index beb8881..845360d 100644
--- a/specs/PKPass.spec.cjs
+++ b/specs/PKPass.spec.cjs
@@ -712,12 +712,12 @@ describe("PKPass", () => {
 
 	describe("expiration date", () => {
 		it("should set a pass expiration date", () => {
-			pkpass.setExpirationDate(new Date(2023, 3, 10));
+			pkpass.setExpirationDate(new Date("2023-04-09T17:00-07:00"));
 
 			const passjsonGenerated = getGeneratedPassJson(pkpass);
 
 			expect(passjsonGenerated.expirationDate).toBe(
-				"2023-04-10T00:00:00Z",
+				"2023-04-10T00:00:00.000Z",
 			);
 		});
 
@@ -808,11 +808,11 @@ describe("PKPass", () => {
 
 	describe("relevant date", () => {
 		it("should set pass relevant date", () => {
-			pkpass.setRelevantDate(new Date(2023, 3, 10, 14, 15));
+			pkpass.setRelevantDate(new Date("2023-04-11T00:15+10:00"));
 
 			const passjsonGenerated = getGeneratedPassJson(pkpass);
 
-			expect(passjsonGenerated.relevantDate).toBe("2023-04-10T14:15:00Z");
+			expect(passjsonGenerated.relevantDate).toBe("2023-04-10T14:15:00.000Z");
 		});
 
 		it("should reset relevant date", () => {
diff --git a/specs/utils.spec.cjs b/specs/utils.spec.cjs
index 3636dd0..9a5ad3e 100644
--- a/specs/utils.spec.cjs
+++ b/specs/utils.spec.cjs
@@ -32,8 +32,8 @@ describe("Utils", () => {
 		});
 
 		it("should convert a Date object to a valid W3C date", () => {
-			expect(processDate(new Date(2020, 6, 1, 0, 0, 0, 0))).toBe(
-				"2020-07-01T00:00:00Z",
+			expect(processDate(new Date("2020-07-01T02:00+02:00"))).toBe(
+				"2020-07-01T00:00:00.000Z",
 			);
 		});
 	});