How to mock a date in Jest and JavaScript?

To set a mock date in Jest and JavaScript, we can use the useFakeTimers and setSystemTime methods.

For instance, we write:

jest
  .useFakeTimers()
  .setSystemTime(new Date('2022-01-01').getTime());

to call useFakeTimers to let us mock timers.

Then we call setSystemTime to set the time of the mock timer by calling it with a timestamp in milliseconds.