I have a test and I am wondering if its strictly necessary or helpful to mock the calendar instance in this case

Here is my test :

@Test
fun determineIsNotInFuture() {
    val fakeTimeRecord = TimeRecord()

    val dateTimeNow = LocalDate.of( 2020 , Month.JANUARY , 1 )
    val dateTimeLater = LocalDate.of(2020, Month.JANUARY, 10)

    var fakeCalendar = Calendar.getInstance()
    fakeCalendar.time = Date.from(dateTimeNow.atStartOfDay(ZoneId.systemDefault()).toInstant())

    fakeTimeRecord.punch = Punch()
    fakeTimeRecord.punch!!.punchIn = Date.from(dateTimeLater.atStartOfDay(ZoneId.systemDefault()).toInstant())

    val isInFuture = timeRecordHelper.determineIfPunchInIsIntheFuture(fakeTimeRecord.getPunchIn(), fakeCalendar)
    assertEquals(true, isInFuture)
}

What I am really trying to test is this time record helper functions returning true correctly when given a know date for the current time and know date for the time punch.

The test runs and tests my function accuratly but I have a new instance of calendar, is there any advantage to mocking the calander instance ?