From 327f40baa8dd52da03f967aea0310351a3d6139c Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Tue, 21 Apr 2026 15:52:51 +0200
Subject: [PATCH 01/13] up

---
 src/lib/date.spec.ts |  6 ++++++
 src/lib/date.ts      | 10 ++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 71a1393..1f46659 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -162,4 +162,10 @@ describe("date tests", () => {
       expect(getLastDayOfYear(date).getTime()).toBe(new Date(2024, 11, 31, 0, 0, 0, 0).getTime());
     }
   });
+
+  test("get ", () => {
+    for (let date = new Date(2024, 0, 1); date < new Date(2025, 0, 1); date.setDate(date.getDate() + 1)) {
+      expect(getLastDayOfYear(date).getTime()).toBe(new Date(2024, 11, 31, 0, 0, 0, 0).getTime());
+    }
+  });
 });
diff --git a/src/lib/date.ts b/src/lib/date.ts
index 8039339..cd40293 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -10,6 +10,7 @@ import {
   startOfDay,
   endOfDay,
   lastDayOfYear,
+  getQuarter,
 } from "date-fns";
 
 /**
@@ -112,3 +113,12 @@ export function getFirstDayOfYear(date: Date): Date {
 export function getLastDayOfYear(date: Date): Date {
   return dateIsValid(date) ? lastDayOfYear(date) : new Date(Number.NaN);
 }
+
+/**
+ * Get the current quarter
+ * @param date The date
+ * @returns the number of the current quarter
+ */
+export function getCurrentQuarter(date: Date): number {
+  return dateIsValid(date) ? getQuarter(date) : Number.NaN;
+}

From 9d123f72690a88b1ab44f55cab6820c65e6e2957 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Tue, 21 Apr 2026 16:03:07 +0200
Subject: [PATCH 02/13] up

---
 CHANGELOG.md         |  1 +
 src/lib/date.spec.ts | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 52990f6..0c96f4f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - `parseEnum` utility function
+- `getCurrentQuarter` utility function
 
 ## [2.2.0] - 2025-10-02
 
diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 1f46659..4589111 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -10,6 +10,7 @@ import {
   getEndOfDay,
   getFirstDayOfYear,
   getLastDayOfYear,
+  getCurrentQuarter,
 } from "./date";
 
 describe("date tests", () => {
@@ -163,9 +164,22 @@ describe("date tests", () => {
     }
   });
 
-  test("get ", () => {
-    for (let date = new Date(2024, 0, 1); date < new Date(2025, 0, 1); date.setDate(date.getDate() + 1)) {
-      expect(getLastDayOfYear(date).getTime()).toBe(new Date(2024, 11, 31, 0, 0, 0, 0).getTime());
-    }
+  test.each([
+    [new Date("2026-01-15"), 1],
+    [new Date("2026-04-10"), 2],
+    [new Date("2026-08-20"), 3],
+    [new Date("2026-11-05"), 4],
+  ])("getCurrentQuarter", (date, expected) => {
+    expect(getCurrentQuarter(date)).toBe(expected);
+  });
+
+  test.each([
+    [null as unknown as Date, Number.NaN],
+    [undefined as unknown as Date, Number.NaN],
+    [42 as unknown as Date, Number.NaN],
+    ["test" as unknown as Date, Number.NaN],
+    [new Date("invalid-date"), Number.NaN],
+  ])("getCurrentQuarter", (date) => {
+    expect(getCurrentQuarter(date)).toBeNaN();
   });
 });

From bb3a08b32f2e8971cf93510f9219a9e467c5c97d Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Tue, 21 Apr 2026 17:30:16 +0200
Subject: [PATCH 03/13] fix changelog

---
 CHANGELOG.md         | 5 ++++-
 src/lib/date.spec.ts | 6 +++---
 src/lib/date.ts      | 6 +++---
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c96f4f..cedfbb7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,12 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `getQuarter` utility function
+
 ## [2.3.0] - 2026-04-07
 
 ### Added
 
 - `parseEnum` utility function
-- `getCurrentQuarter` utility function
 
 ## [2.2.0] - 2025-10-02
 
diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 4589111..45813cf 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -10,7 +10,7 @@ import {
   getEndOfDay,
   getFirstDayOfYear,
   getLastDayOfYear,
-  getCurrentQuarter,
+  getQuarter,
 } from "./date";
 
 describe("date tests", () => {
@@ -170,7 +170,7 @@ describe("date tests", () => {
     [new Date("2026-08-20"), 3],
     [new Date("2026-11-05"), 4],
   ])("getCurrentQuarter", (date, expected) => {
-    expect(getCurrentQuarter(date)).toBe(expected);
+    expect(getQuarter(date)).toBe(expected);
   });
 
   test.each([
@@ -180,6 +180,6 @@ describe("date tests", () => {
     ["test" as unknown as Date, Number.NaN],
     [new Date("invalid-date"), Number.NaN],
   ])("getCurrentQuarter", (date) => {
-    expect(getCurrentQuarter(date)).toBeNaN();
+    expect(getQuarter(date)).toBeNaN();
   });
 });
diff --git a/src/lib/date.ts b/src/lib/date.ts
index cd40293..4ad6681 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -10,7 +10,7 @@ import {
   startOfDay,
   endOfDay,
   lastDayOfYear,
-  getQuarter,
+  getQuarter as getQuarterInternal,
 } from "date-fns";
 
 /**
@@ -119,6 +119,6 @@ export function getLastDayOfYear(date: Date): Date {
  * @param date The date
  * @returns the number of the current quarter
  */
-export function getCurrentQuarter(date: Date): number {
-  return dateIsValid(date) ? getQuarter(date) : Number.NaN;
+export function getQuarter(date: Date): number {
+  return dateIsValid(date) ? getQuarterInternal(date) : Number.NaN;
 }

From 7cf6e07546564af5161bb1fc77a4e33fbf1c686c Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Tue, 21 Apr 2026 17:32:49 +0200
Subject: [PATCH 04/13] up

---
 src/lib/date.spec.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 45813cf..c571614 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -169,7 +169,7 @@ describe("date tests", () => {
     [new Date("2026-04-10"), 2],
     [new Date("2026-08-20"), 3],
     [new Date("2026-11-05"), 4],
-  ])("getCurrentQuarter", (date, expected) => {
+  ])("getQuarter", (date, expected) => {
     expect(getQuarter(date)).toBe(expected);
   });
 
@@ -179,7 +179,7 @@ describe("date tests", () => {
     [42 as unknown as Date, Number.NaN],
     ["test" as unknown as Date, Number.NaN],
     [new Date("invalid-date"), Number.NaN],
-  ])("getCurrentQuarter", (date) => {
+  ])("getQuarter", (date) => {
     expect(getQuarter(date)).toBeNaN();
   });
 });

From 3a7cf45b46558b629dc66bb8b8ea6da66cbab35b Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Tue, 21 Apr 2026 17:33:31 +0200
Subject: [PATCH 05/13] up

---
 src/lib/date.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lib/date.ts b/src/lib/date.ts
index 4ad6681..2567f85 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -115,9 +115,9 @@ export function getLastDayOfYear(date: Date): Date {
 }
 
 /**
- * Get the current quarter
+ * Get the quarter
  * @param date The date
- * @returns the number of the current quarter
+ * @returns the number of the quarter
  */
 export function getQuarter(date: Date): number {
   return dateIsValid(date) ? getQuarterInternal(date) : Number.NaN;

From 6436273cb4618096cd0179ce753fe23b1b726d64 Mon Sep 17 00:00:00 2001
From: dom-baur <dominic.baur@collana.com>
Date: Wed, 22 Apr 2026 08:15:09 +0200
Subject: [PATCH 06/13] Update src/lib/date.ts

Co-authored-by: Daniele Debernardi <drebrez@gmail.com>
---
 src/lib/date.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/date.ts b/src/lib/date.ts
index 2567f85..bb982a0 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -117,7 +117,7 @@ export function getLastDayOfYear(date: Date): Date {
 /**
  * Get the quarter
  * @param date The date
- * @returns the number of the quarter
+ * @returns The year quarter
  */
 export function getQuarter(date: Date): number {
   return dateIsValid(date) ? getQuarterInternal(date) : Number.NaN;

From a1784a5fa74b643027602dbff32eb6a808106d5c Mon Sep 17 00:00:00 2001
From: dom-baur <dominic.baur@collana.com>
Date: Wed, 22 Apr 2026 08:15:22 +0200
Subject: [PATCH 07/13] Update src/lib/date.ts

Co-authored-by: Daniele Debernardi <drebrez@gmail.com>
---
 src/lib/date.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/date.ts b/src/lib/date.ts
index bb982a0..48c0476 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -115,7 +115,7 @@ export function getLastDayOfYear(date: Date): Date {
 }
 
 /**
- * Get the quarter
+ * Get the year quarter for the given date
  * @param date The date
  * @returns The year quarter
  */

From ae321e52d52604b2c49a67a64292c62a8626ea3e Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 22 Apr 2026 08:20:07 +0200
Subject: [PATCH 08/13] Update test

---
 src/lib/date.spec.ts | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index c571614..7a5072a 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -165,6 +165,11 @@ describe("date tests", () => {
   });
 
   test.each([
+    [null as unknown as Date, Number.NaN],
+    [undefined as unknown as Date, Number.NaN],
+    [42 as unknown as Date, Number.NaN],
+    ["test" as unknown as Date, Number.NaN],
+    [new Date("invalid-date"), Number.NaN],
     [new Date("2026-01-15"), 1],
     [new Date("2026-04-10"), 2],
     [new Date("2026-08-20"), 3],
@@ -172,14 +177,4 @@ describe("date tests", () => {
   ])("getQuarter", (date, expected) => {
     expect(getQuarter(date)).toBe(expected);
   });
-
-  test.each([
-    [null as unknown as Date, Number.NaN],
-    [undefined as unknown as Date, Number.NaN],
-    [42 as unknown as Date, Number.NaN],
-    ["test" as unknown as Date, Number.NaN],
-    [new Date("invalid-date"), Number.NaN],
-  ])("getQuarter", (date) => {
-    expect(getQuarter(date)).toBeNaN();
-  });
 });

From 3f385fa28b9d98d2e75cd789f55b2c19f4d082ed Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 22 Apr 2026 10:02:32 +0200
Subject: [PATCH 09/13] up

---
 CHANGELOG.md         |  1 +
 src/lib/date.spec.ts | 24 +++++++++++++++++++++---
 src/lib/date.ts      | 13 +++++++++++++
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cedfbb7..0a0b827 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - `getQuarter` utility function
+- `getPreviousQuarter` utility function
 
 ## [2.3.0] - 2026-04-07
 
diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 7a5072a..b0dfe95 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -11,18 +11,16 @@ import {
   getFirstDayOfYear,
   getLastDayOfYear,
   getQuarter,
+  getPreviousQuarter,
 } from "./date";
 
 describe("date tests", () => {
   test.each([
-    // Valid dates
     [new Date(), true],
     [new Date(new Date()), true],
     [new Date("2014-03-15"), true],
     [new Date(2014, 3, 15), true],
     [new Date(42), true],
-
-    // Invalid dates
     [new Date(Number.MAX_VALUE), false],
     [new Date(Number.NaN), false],
     [new Date("2014-03-36"), false],
@@ -177,4 +175,24 @@ describe("date tests", () => {
   ])("getQuarter", (date, expected) => {
     expect(getQuarter(date)).toBe(expected);
   });
+
+  test.each([[null as unknown as Date], [undefined as unknown as Date], [42 as unknown as Date], ["test" as unknown as Date]])(
+    "getQuarter invalid inputs",
+    (date) => {
+      expect(getQuarter(date)).toBeNaN();
+    },
+  );
+
+  test.each([
+    [new Date("2026-01-15"), 4],
+    [new Date("2026-04-10"), 1],
+    [new Date("2026-08-20"), 2],
+    [new Date("2026-11-05"), 3],
+  ])("getPreviousQuarter", (date, expected) => {
+    expect(getPreviousQuarter(date)).toBe(expected);
+  });
+
+  test.each([null, undefined, 42, "test", new Date("invalid-date")] as unknown as Date[])("getPreviousQuarter invalid inputs", (date) => {
+    expect(getPreviousQuarter(date)).toBeNaN();
+  });
 });
diff --git a/src/lib/date.ts b/src/lib/date.ts
index 48c0476..744a019 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -122,3 +122,16 @@ export function getLastDayOfYear(date: Date): Date {
 export function getQuarter(date: Date): number {
   return dateIsValid(date) ? getQuarterInternal(date) : Number.NaN;
 }
+
+/**
+ * Get the previous year quarter for the given date
+ * @param date The date
+ * @returns The previous year quarter
+ */
+export function getPreviousQuarter(date: Date): number {
+  if (!dateIsValid(date)) return Number.NaN;
+
+  const currentQuarter = getQuarter(date);
+
+  return currentQuarter === 1 ? 4 : currentQuarter - 1;
+}

From 70ea670fae144a341b142c32296258c93511a019 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 22 Apr 2026 10:19:38 +0200
Subject: [PATCH 10/13] up

---
 src/lib/date.spec.ts | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index b0dfe95..e8f5458 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -16,6 +16,7 @@ import {
 
 describe("date tests", () => {
   test.each([
+    // Valid dates
     [new Date(), true],
     [new Date(new Date()), true],
     [new Date("2014-03-15"), true],
@@ -24,6 +25,8 @@ describe("date tests", () => {
     [new Date(Number.MAX_VALUE), false],
     [new Date(Number.NaN), false],
     [new Date("2014-03-36"), false],
+
+    // Invalid dates
     [null as unknown as Date, false],
     [undefined as unknown as Date, false],
     [42 as unknown as Date, false],
@@ -176,13 +179,6 @@ describe("date tests", () => {
     expect(getQuarter(date)).toBe(expected);
   });
 
-  test.each([[null as unknown as Date], [undefined as unknown as Date], [42 as unknown as Date], ["test" as unknown as Date]])(
-    "getQuarter invalid inputs",
-    (date) => {
-      expect(getQuarter(date)).toBeNaN();
-    },
-  );
-
   test.each([
     [new Date("2026-01-15"), 4],
     [new Date("2026-04-10"), 1],
@@ -192,7 +188,11 @@ describe("date tests", () => {
     expect(getPreviousQuarter(date)).toBe(expected);
   });
 
-  test.each([null, undefined, 42, "test", new Date("invalid-date")] as unknown as Date[])("getPreviousQuarter invalid inputs", (date) => {
-    expect(getPreviousQuarter(date)).toBeNaN();
-  });
+  test.each([[null as unknown as Date], [undefined as unknown as Date], [42 as unknown as Date], ["test" as unknown as Date]])(
+    "getQuarter and getPreviousQuarter invalid inputs",
+    (date) => {
+      expect(getQuarter(date)).toBeNaN();
+      expect(getPreviousQuarter(date)).toBeNaN();
+    },
+  );
 });

From ca15a47f06b08d07b9ef3224dd6442d4b5d21bf1 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 29 Apr 2026 15:29:17 +0200
Subject: [PATCH 11/13] up

---
 CHANGELOG.md         |  2 +-
 src/lib/date.spec.ts | 35 +++++++++++++++++++----------------
 src/lib/date.ts      | 14 ++++++--------
 3 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0a0b827..ff51720 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,7 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - `getQuarter` utility function
-- `getPreviousQuarter` utility function
+- `addQuarters` utility function
 
 ## [2.3.0] - 2026-04-07
 
diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index e8f5458..563174c 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable max-lines */
 import {
   dateIsValid,
   dateIsFirstDayOfMonth,
@@ -10,8 +11,8 @@ import {
   getEndOfDay,
   getFirstDayOfYear,
   getLastDayOfYear,
+  addQuarters,
   getQuarter,
-  getPreviousQuarter,
 } from "./date";
 
 describe("date tests", () => {
@@ -180,19 +181,21 @@ describe("date tests", () => {
   });
 
   test.each([
-    [new Date("2026-01-15"), 4],
-    [new Date("2026-04-10"), 1],
-    [new Date("2026-08-20"), 2],
-    [new Date("2026-11-05"), 3],
-  ])("getPreviousQuarter", (date, expected) => {
-    expect(getPreviousQuarter(date)).toBe(expected);
-  });
-
-  test.each([[null as unknown as Date], [undefined as unknown as Date], [42 as unknown as Date], ["test" as unknown as Date]])(
-    "getQuarter and getPreviousQuarter invalid inputs",
-    (date) => {
-      expect(getQuarter(date)).toBeNaN();
-      expect(getPreviousQuarter(date)).toBeNaN();
-    },
-  );
+    [new Date(2026, 4, 29), 1, new Date(2026, 7, 29)],
+    [new Date(2026, 4, 29), 4, new Date(2027, 4, 29)],
+    [new Date(2026, 8, 15), -1, new Date(2026, 5, 15)],
+    [new Date(2026, 8, 15), -4, new Date(2025, 8, 15)],
+  ])("addQuarters", (date, amount, expected) => {
+    expect(addQuarters(date, amount).getTime()).toBe(expected.getTime());
+  });
+
+  test.each([
+    [null as unknown as Date, 1],
+    [undefined as unknown as Date, -1],
+    [42 as unknown as Date, 1],
+    ["test" as unknown as Date, -1],
+    [new Date("invalid-date"), 1],
+  ])("addQuarters with invalid inputs", (date, amount) => {
+    expect(addQuarters(date, amount).getTime()).toBe(Number.NaN);
+  });
 });
diff --git a/src/lib/date.ts b/src/lib/date.ts
index 744a019..b91f628 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -11,6 +11,7 @@ import {
   endOfDay,
   lastDayOfYear,
   getQuarter as getQuarterInternal,
+  addQuarters as addQuartersInternal,
 } from "date-fns";
 
 /**
@@ -124,14 +125,11 @@ export function getQuarter(date: Date): number {
 }
 
 /**
- * Get the previous year quarter for the given date
+ * Shifts a date by a given number of quarters.
  * @param date The date
- * @returns The previous year quarter
+ * @param amount Number of quarters to shift by (negative values shift the date backwards)
+ * @returns A new Date shifted by the specified number of quarters
  */
-export function getPreviousQuarter(date: Date): number {
-  if (!dateIsValid(date)) return Number.NaN;
-
-  const currentQuarter = getQuarter(date);
-
-  return currentQuarter === 1 ? 4 : currentQuarter - 1;
+export function addQuarters(date: Date, amount: number): Date {
+  return dateIsValid(date) ? addQuartersInternal(date, amount) : new Date(Number.NaN);
 }

From ff52f5a9f68dcebedb9f9ea3598439bb93e2f210 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 29 Apr 2026 15:41:32 +0200
Subject: [PATCH 12/13] up

---
 src/lib/date.spec.ts | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 563174c..7da5195 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -1,4 +1,3 @@
-/* eslint-disable max-lines */
 import {
   dateIsValid,
   dateIsFirstDayOfMonth,
@@ -181,6 +180,12 @@ describe("date tests", () => {
   });
 
   test.each([
+    [null as unknown as Date, 1, new Date(Number.NaN)],
+    [undefined as unknown as Date, -1, new Date(Number.NaN)],
+    [42 as unknown as Date, 1, new Date(Number.NaN)],
+    ["test" as unknown as Date, -1, new Date(Number.NaN)],
+    [new Date("invalid-date"), 1, new Date(Number.NaN)],
+    [new Date(Number.NaN), 1, new Date(Number.NaN)],
     [new Date(2026, 4, 29), 1, new Date(2026, 7, 29)],
     [new Date(2026, 4, 29), 4, new Date(2027, 4, 29)],
     [new Date(2026, 8, 15), -1, new Date(2026, 5, 15)],
@@ -188,14 +193,4 @@ describe("date tests", () => {
   ])("addQuarters", (date, amount, expected) => {
     expect(addQuarters(date, amount).getTime()).toBe(expected.getTime());
   });
-
-  test.each([
-    [null as unknown as Date, 1],
-    [undefined as unknown as Date, -1],
-    [42 as unknown as Date, 1],
-    ["test" as unknown as Date, -1],
-    [new Date("invalid-date"), 1],
-  ])("addQuarters with invalid inputs", (date, amount) => {
-    expect(addQuarters(date, amount).getTime()).toBe(Number.NaN);
-  });
 });

From 9268b4ddeb26cfa806681379532387b00b085450 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 29 Apr 2026 15:46:35 +0200
Subject: [PATCH 13/13] up

---
 src/lib/date.spec.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 7da5195..b2336f1 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -22,11 +22,11 @@ describe("date tests", () => {
     [new Date("2014-03-15"), true],
     [new Date(2014, 3, 15), true],
     [new Date(42), true],
+
+    // Invalid dates
     [new Date(Number.MAX_VALUE), false],
     [new Date(Number.NaN), false],
     [new Date("2014-03-36"), false],
-
-    // Invalid dates
     [null as unknown as Date, false],
     [undefined as unknown as Date, false],
     [42 as unknown as Date, false],