Added timezones functions

.github/workflows/ci.yml

@@ -89,6 +89,8 @@ jobs:
       - run: yarn lint
       - run: yarn build
       - run: yarn jest
+        env:
+          TZ: Europe/Zurich
 
       - name: Code Coverage Summary Report
         uses: irongut/CodeCoverageSummary@v1.3.0

.nvmrc

@@ -0,0 +1 @@
+18

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `getDateWithoutTimeZone` utility function
+- `getDateAddTimeZone` utility function
+
 ## [2.4.0] - 2026-04-29
 
 ### Added

eslint.config.ts

@@ -6,4 +6,8 @@ export default [
     jest: true,
     jsdocRequireJsdoc: true,
   }),
+  {
+    files: ["src/lib/*.spec.ts"],
+    rules: { "max-lines": ["off"] },
+  },
 ];

package.json

@@ -34,7 +34,7 @@
     "prettier-check": "prettier --check .",
     "prettier-write": "prettier --write .",
     "start": "rollup -c -w",
-    "test": "yarn jest",
+    "test": "cross-env TZ=Europe/Zurich yarn jest",
     "start-all": "concurrently \"yarn start\" \"yarn start-yalc\"",
     "start-yalc": "yarn nodemon --watch dist -x \"yarn yalc push\""
   },
@@ -53,6 +53,7 @@
     "@types/rollup-plugin-peer-deps-external": "^2.2.5",
     "@types/uuid": "^9.0.7",
     "concurrently": "^8.0.1",
+    "cross-env": "^7.0.3",
     "eslint": "^9.24.0",
     "jest": "^29.6.1",
     "jest-localstorage-mock": "^2.4.26",

src/lib/date.spec.ts

@@ -12,6 +12,8 @@ import {
   getLastDayOfYear,
   addQuarters,
   getQuarter,
+  getDateAddTimeZone,
+  getDateWithoutTimeZone,
 } from "./date";
 
 describe("date tests", () => {
@@ -193,4 +195,32 @@ describe("date tests", () => {
   ])("addQuarters", (date, amount, expected) => {
     expect(addQuarters(date, amount).getTime()).toBe(expected.getTime());
   });
+
+  test.each([
+    [null as unknown as Date, new Date(Number.NaN)],
+    [undefined as unknown as Date, new Date(Number.NaN)],
+    [42 as unknown as Date, new Date(Number.NaN)],
+    ["2015-03-15" as unknown as Date, new Date(Number.NaN)],
+    [{ year: 2014, month: 2, day: 15 } as unknown as Date, new Date(Number.NaN)],
+    [new Date(2026, 6, 5, 0, 0, 0, 0), new Date(2026, 6, 5, 0, 0, 0, 0 + 120 * 60_000)],
+    [new Date(2026, 6, 5, 1, 12, 13, 1), new Date(2026, 6, 5, 1, 12, 13, 1 + 120 * 60_000)],
+    [new Date(2026, 12, 5, 0, 0, 0, 0), new Date(2026, 12, 5, 0, 0, 0, 0 + 60 * 60_000)],
+    [new Date(2026, 12, 5, 1, 12, 13, 1), new Date(2026, 12, 5, 1, 12, 13, 1 + 60 * 60_000)],
+  ])("getDateWithoutTimeZone", (date, expected) => {
+    expect(getDateWithoutTimeZone(date).getTime()).toBe(expected.getTime());
+  });
+
+  test.each([
+    [null as unknown as Date, new Date(Number.NaN)],
+    [undefined as unknown as Date, new Date(Number.NaN)],
+    [42 as unknown as Date, new Date(Number.NaN)],
+    ["2015-03-15" as unknown as Date, new Date(Number.NaN)],
+    [{ year: 2014, month: 2, day: 15 } as unknown as Date, new Date(Number.NaN)],
+    [new Date(2026, 6, 5, 0, 0, 0, 0), new Date(2026, 6, 5, 0, 0, 0, 0 - 120 * 60_000)],
+    [new Date(2026, 6, 5, 1, 12, 13, 1), new Date(2026, 6, 5, 1, 12, 13, 1 - 120 * 60_000)],
+    [new Date(2026, 12, 5, 0, 0, 0, 0), new Date(2026, 12, 5, 0, 0, 0, 0 - 60 * 60_000)],
+    [new Date(2026, 12, 5, 1, 12, 13, 1), new Date(2026, 12, 5, 1, 12, 13, 1 - 60 * 60_000)],
+  ])("getDateAddTimeZone", (date, expected) => {
+    expect(getDateAddTimeZone(date).getTime()).toBe(expected.getTime());
+  });
 });

src/lib/date.ts

@@ -133,3 +133,21 @@ export function getQuarter(date: Date): number {
 export function addQuarters(date: Date, amount: number): Date {
   return dateIsValid(date) ? addQuartersInternal(date, amount) : new Date(Number.NaN);
 }
+
+/**
+ * Get the date removing the time-zone offset
+ * @param date The date
+ * @returns the given date removing the time-zone offset
+ */
+export function getDateWithoutTimeZone(date: Date): Date {
+  return dateIsValid(date) ? new Date(date.getTime() - date.getTimezoneOffset() * 60_000) : new Date(Number.NaN);
+}
+
+/**
+ * Get the date adding the time-zone offset
+ * @param date The date
+ * @returns the given date adding the time-zone offset
+ */
+export function getDateAddTimeZone(date: Date): Date {
+  return dateIsValid(date) ? new Date(date.getTime() + date.getTimezoneOffset() * 60_000) : new Date(Number.NaN);
+}

yarn.lock

@@ -2401,7 +2401,14 @@ create-require@^1.1.0:
   resolved "https://registry.yarnpkg.com/create-require/-/create-require-1.1.1.tgz#c1d7e8f1e5f6cfc9ff65f9cd352d37348756c333"
   integrity sha512-dcKFX3jn0MpIaXjisoRvexIJVEKzaq7z2rZKxf+MSr9TkdmHmsU4m2lcLojrj/FHl8mk5VxMmYA+ftRkP/3oKQ==
 
-cross-spawn@^7.0.3, cross-spawn@^7.0.6:
+cross-env@^7.0.3:
+  version "7.0.3"
+  resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-7.0.3.tgz#865264b29677dc015ba8418918965dd232fc54cf"
+  integrity sha512-+/HKd6EgcQCJGh2PSjZuUitQBQynKor4wrFbRg4DtAgS1aWO+gU52xpH7M9ScGgXSYmAVS9bIJ8EzuaGw0oNAw==
+  dependencies:
+    cross-spawn "^7.0.1"
+
+cross-spawn@^7.0.1, cross-spawn@^7.0.3, cross-spawn@^7.0.6:
   version "7.0.6"
   resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-7.0.6.tgz#8a58fe78f00dcd70c370451759dfbfaf03e8ee9f"
   integrity sha512-uV2QOWP2nWzsy2aMp8aRibhi9dlzF5Hgh5SHaB9OiTGEyDTiJJyx0uy51QXdyWbtAHNua4XJzUKca3OzKUd3vA==