test: time difference with time zone (#22782)

docs/development/local-development.md

@@ -29,6 +29,10 @@ sudo apt-get update
 sudo apt-get install -y git build-essential nodejs yarn
 ```
 
+#### Nix
+
+To enter a development shell with the necessary packages, run `nix-shell --packages gcc gitFull nodejs yarn`.
+
 #### Windows
 
 Follow these steps to set up your development environment on Windows 10.

lib/util/date.spec.ts

@@ -7,7 +7,7 @@ import {
 } from './date';
 
 describe('util/date', () => {
-  const t0 = DateTime.fromISO('2020-10-10');
+  const t0 = DateTime.fromISO('2020-10-10', { zone: 'utc' });
 
   beforeAll(() => {
     jest.useFakeTimers();