 TST #24444 converting Period to Timestamp
I've tested intervals `ms`, `s` and `min`.
Note: the test raises an error for `ms` on v1.0.3, but is successful on master
Note: I did not choose to close this issue has the test fail for `ns` unit

[ ] #24444
[ 1 ] tests added / passed
[ x ] passes `black pandas`
[ x ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

As per your comment and my last comment on #24444, I think a good tests could be like the ones below. However, no one is passing correctly.

```
@pytest.mark.parametrize("period_str, freq, expected",
        [
            ("2000-12-31 23:59:59.999999", "ms", 999999),
            ("2001-01-01 00:00:00.000001", "ms", 1),
        ],
    )
    def test_to_timestamp_precision_ms(self, period_str, freq, expected):
        # GH 24444
        result = Period(period_str).to_timestamp(freq=freq)
        assert result.microsecond == expected

@pytest.mark.parametrize( "period_str, freq, expected",
        [
            ("2000-12-31 23:59:59.999999999", "ns", 999999999),
            ("2001-01-01 00:00:00.000000001", "ns", 1),
        ],
    )
    def test_to_timestamp_precision_ns(self, period_str, freq, expected):
        # GH 24444
        result = Period(period_str).to_timestamp(freq=freq)
        assert result.nanosecond == expected
``` @OlivierLuG these are just tests. but is this issue actually fixed? The issues are notre fixed. The tests all fail on master.
The flag `need test` mislead me. I've updated the main topic. Perhaps the flag `bug` is more appropriate.
Note: I tried to find a beginning point for this issue, but this is beyond my kwnoledge. I've managed to resolve the microsecond issue + added test.
I've made a new PR to update master. Sorry, there iare conflict. I don't know how to handle that.
[x] closes #24444 
[x] `black pandas` passed
[x] news tests added
[x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Note, I'll will raise a new Issue. The `nanosecond` method returns `0` whatever I try. 