fix(date): keep past and future within the year range when refDate is a leap day

src/modules/date/_utils.ts

@@ -0,0 +1,16 @@
+/**
+ * Returns the timestamp of the given date moved to the given year (in UTC).
+ * February 29 becomes February 28 in a common year instead of rolling over to March 1.
+ *
+ * @param date The date to move.
+ * @param year The year to move the date to.
+ */
+export function sameDayInYear(date: Date, year: number): number {
+  const result = new Date(date);
+  result.setUTCFullYear(year);
+  if (result.getUTCMonth() !== date.getUTCMonth()) {
+    result.setUTCDate(0);
+  }
+
+  return result.getTime();
+}

src/modules/date/birthdate.ts

@@ -2,26 +2,9 @@ import type { FakerCore } from '../../core';
 import { FakerError } from '../../errors/faker-error';
 import { toDate } from '../../internal/date';
 import { getDefaultRefDate } from '../../utils/get-default-ref-date';
+import { sameDayInYear } from './_utils';
 import { fakeDateBetween } from './between';
 
-/**
- * Returns the timestamp of the given date moved to the given year.
- * February 29 becomes February 28 in a common year instead of rolling over to March 1,
- * so a person born on the returned day has their birthday on or before the given date.
- *
- * @param date The date to move.
- * @param year The year to move the date to.
- */
-function sameDayInYear(date: Date, year: number): number {
-  const result = new Date(date);
-  result.setUTCFullYear(year);
-  if (result.getUTCMonth() !== date.getUTCMonth()) {
-    result.setUTCDate(0);
-  }
-
-  return result.getTime();
-}
-
 /**
  * Returns a random birthdate. By default, the birthdate is generated for an adult between 18 and 80 years old.
  * But you can customize the `'age'` range or the `'year'` range to generate a more specific birthdate.

src/modules/date/future.ts

@@ -3,6 +3,7 @@ import { FakerError } from '../../errors/faker-error';
 import { toDate } from '../../internal/date';
 import { getDefaultRefDate } from '../../utils/get-default-ref-date';
 import type { NumberOrRange } from '../../utils/types';
+import { sameDayInYear } from './_utils';
 import { fakeDateBetween } from './between';
 
 /**
@@ -62,10 +63,12 @@ export function fakeDateFuture(
   }
 
   const time = toDate(refDate);
+  const year = time.getUTCFullYear();
+  // A February 29 refDate moves to March 1 for the earliest date (at least
+  // `years.min` years) and to February 28 for the latest one (still within `years.max` years).
   const from = new Date(time);
-  from.setUTCFullYear(from.getUTCFullYear() + years.min);
-  const to = new Date(time);
-  to.setUTCFullYear(to.getUTCFullYear() + years.max);
+  from.setUTCFullYear(year + years.min);
+  const to = sameDayInYear(time, year + years.max);
 
   return fakeDateBetween(fakerCore, {
     from: from.getTime() + 1000,

src/modules/date/past.ts

@@ -3,6 +3,7 @@ import { FakerError } from '../../errors/faker-error';
 import { toDate } from '../../internal/date';
 import { getDefaultRefDate } from '../../utils/get-default-ref-date';
 import type { NumberOrRange } from '../../utils/types';
+import { sameDayInYear } from './_utils';
 import { fakeDateBetween } from './between';
 
 /**
@@ -62,13 +63,15 @@ export function fakeDatePast(
   }
 
   const time = toDate(refDate);
+  const year = time.getUTCFullYear();
+  // A February 29 refDate moves to March 1 for the earliest date (still within
+  // `years.max` years) and to February 28 for the latest one (at least `years.min` years).
   const from = new Date(time);
-  from.setUTCFullYear(from.getUTCFullYear() - years.max);
-  const to = new Date(time);
-  to.setUTCFullYear(to.getUTCFullYear() - years.min);
+  from.setUTCFullYear(year - years.max);
+  const to = sameDayInYear(time, year - years.min);
 
   return fakeDateBetween(fakerCore, {
     from,
-    to: to.getTime() - 1000,
+    to: to - 1000,
   });
 }

test/modules/date.spec.ts

@@ -248,6 +248,44 @@ describe('date', () => {
           expect(date).toEqual(new Date(Date.UTC(1980, 2, 1)));
         });
 
+        it('should return a date at least min years in the past when the refDate is a leap day', () => {
+          const customFaker = new SimpleFaker({
+            randomizer: {
+              next() {
+                return MERSENNE_MAX_VALUE;
+              },
+              seed() {},
+            },
+          });
+
+          const date = customFaker.date.past({
+            years: { min: 1, max: 2 },
+            refDate: new Date(Date.UTC(2024, 1, 29, 12)),
+          });
+
+          // One year before 2024-02-29 is 2023-02-28, not 2023-03-01.
+          expect(date).toEqual(new Date(Date.UTC(2023, 1, 28, 11, 59, 59)));
+        });
+
+        it('should return a date at most max years in the past when the refDate is a leap day', () => {
+          const customFaker = new SimpleFaker({
+            randomizer: {
+              next() {
+                return 0;
+              },
+              seed() {},
+            },
+          });
+
+          const date = customFaker.date.past({
+            years: { min: 1, max: 2 },
+            refDate: new Date(Date.UTC(2024, 1, 29, 12)),
+          });
+
+          // 2022-02-28 would be more than two years before 2024-02-29.
+          expect(date).toEqual(new Date(Date.UTC(2022, 2, 1, 12)));
+        });
+
         it('should throw an error when years = 0', () => {
           const refDate = new Date();
           expect(() =>
@@ -368,6 +406,44 @@ describe('date', () => {
           expect(date).toEqual(new Date(Date.UTC(2060, 2, 1)));
         });
 
+        it('should return a date at least min years in the future when the refDate is a leap day', () => {
+          const customFaker = new SimpleFaker({
+            randomizer: {
+              next() {
+                return 0;
+              },
+              seed() {},
+            },
+          });
+
+          const date = customFaker.date.future({
+            years: { min: 1, max: 2 },
+            refDate: new Date(Date.UTC(2024, 1, 29, 12)),
+          });
+
+          // 2025-02-28 would be less than one year after 2024-02-29.
+          expect(date).toEqual(new Date(Date.UTC(2025, 2, 1, 12, 0, 1)));
+        });
+
+        it('should return a date at most max years in the future when the refDate is a leap day', () => {
+          const customFaker = new SimpleFaker({
+            randomizer: {
+              next() {
+                return MERSENNE_MAX_VALUE;
+              },
+              seed() {},
+            },
+          });
+
+          const date = customFaker.date.future({
+            years: { min: 1, max: 2 },
+            refDate: new Date(Date.UTC(2024, 1, 29, 12)),
+          });
+
+          // Two years after 2024-02-29 is 2026-02-28, not 2026-03-01.
+          expect(date).toEqual(new Date(Date.UTC(2026, 1, 28, 12)));
+        });
+
         it('should throw an error when years = 0', () => {
           const refDate = new Date();
           expect(() =>