How to use jest.useFakeTimers('modern') and jest.setSystemTime() to test current time

Node
1

Test-Driven Development: 11- Testing the ReturnDate

Mosh shows how to measure the difference of two dates to test current time. I wonder if there are other ways to test current time, then I found jest.useFakeTimers(‘modern’) and jest.setSystemTime() but I don’t know why it breaks my test.
Does anyone know how to work with these two helpers?

If I add them after the assertion, the test will pass

it('should set dateReturned if input is valid', async () => {
    await exec()

    const rentalInDb = await Rental.findById(rental._id)
    const diff = new Date() - rentalInDb.dateReturned

    expect(diff).toBeLessThan(10 * 1000)

    jest.useFakeTimers('modern')
    jest.setSystemTime(new Date('20 Aug 2020 00:12:00 GMT').getTime())

    console.log(rentalInDb.dateReturned)
    console.log(new Date())

    jest.useRealTimers()
  }, 60000)

If I add them in the beginning of the assertion, the test will fail

  it('should set dateReturned if input is valid', async () => {
    jest.useFakeTimers('modern') // moved to the start of the test
    jest.setSystemTime(new Date('20 Aug 2020 00:12:00 GMT').getTime()) // moved to the start of the test

    await exec()

    const rentalInDb = await Rental.findById(rental._id)
    const diff = new Date() - rentalInDb.dateReturned

    expect(diff).toBeLessThan(10 * 1000)

    console.log(rentalInDb.dateReturned)
    console.log(new Date())

    jest.useRealTimers()
  }, 60000)

error message

● /api/returns › should set dateReturned if input is valid

    thrown: "Exceeded timeout of 5000 ms for a hook.
    Use jest.setTimeout(newTimeout) to increase the timeout value, if this is a long-running test."

      49 |   })
      50 |
    > 51 |   afterEach(async () => {
         |   ^
      52 |     await Rental.remove({})
      53 |     await server.close()
      54 |   })

      at tests/integration/return.test.js:51:3
      at Object.<anonymous> (tests/integration/return.test.js:6:1)
          at runMicrotasks (<anonymous>)
      at TestScheduler.scheduleTests (node_modules/@jest/core/build/TestScheduler.js:333:13)
      at runJest (node_modules/@jest/core/build/runJest.js:387:19)