Removing timezone offsets before formatting/parsing date-time strings with `date-fns`, etc.

index.test.ts

import { describe, expect, it } from "vitest";
import { removeTimezoneOffset } from ".";

describe("removeTimezoneOffset", () => {
  it("should remove timezone offset in format -07:00", () => {
    const dateTime = "2024-06-15T17:30:00-07:00";
    const expected = "2024-06-15T17:30:00";
    expect(removeTimezoneOffset(dateTime)).toBe(expected);
  });

  it("should remove timezone offset in format +07:00", () => {
    const dateTime = "2024-06-15T17:30:00+07:00";
    const expected = "2024-06-15T17:30:00";
    expect(removeTimezoneOffset(dateTime)).toBe(expected);
  });

  it("should remove timezone offset in format -0700", () => {
    const dateTime = "2024-06-15T17:30:00-0700";
    const expected = "2024-06-15T17:30:00";
    expect(removeTimezoneOffset(dateTime)).toBe(expected);
  });

  it("should remove timezone offset in format +0700", () => {
    const dateTime = "2024-06-15T17:30:00+0700";
    const expected = "2024-06-15T17:30:00";
    expect(removeTimezoneOffset(dateTime)).toBe(expected);
  });

  it("should remove milliseconds and Z", () => {
    const dateTime = "2019-12-15T20:00:00.000Z";
    const expected = "2019-12-15T20:00:00";
    expect(removeTimezoneOffset(dateTime)).toBe(expected);
  });
});

remove-tz-offsets.ts

export function removeTimezoneOffset(dateTime: string): string {
  return dateTime.replace(
    /-\d{2}:\d{2}$|\+\d{2}:\d{2}$|-\d{4}$|\+\d{4}$|\.\d+Z$/,
    "",
  );
}