fix: correct handling of day in date

src/pad-with-leading-zero.spec.ts

@@ -0,0 +1,11 @@
+import { padWithLeadingZero } from "./pad-with-leading-zero";
+
+describe("Pad with leading zero", () => {
+  it("should pad a single digit with a leading zero", () => {
+    expect(padWithLeadingZero(4)).toBe("04");
+  });
+
+  it("should not pad a double digit number", () => {
+    expect(padWithLeadingZero(14)).toBe("14");
+  });
+});

src/pad-with-leading-zero.ts

@@ -0,0 +1,4 @@
+export function padWithLeadingZero(n: number) {
+  const retval = `0${n}`;
+  return retval.slice(-2);
+}

src/parse-date-of-birth.ts

@@ -1,3 +1,5 @@
+import { padWithLeadingZero } from "./pad-with-leading-zero";
+
 export function parseDateOfBirth(dateOfBirth: string): Date {
   const year = +dateOfBirth.substr(0, 4);
   const month = dateOfBirth.substr(4, 2);
@@ -6,5 +8,5 @@ export function parseDateOfBirth(dateOfBirth: string): Date {
   if (day >= 32) {
     day -= 60;
   }
-  return new Date(`${year}-${month}-${day}`);
+  return new Date(`${year}-${month}-${padWithLeadingZero(day)}`);
 }