Sounds like the issue is on ArrangeData server action.
Once changed it to JSONSerailize all the NULL date has been displayed correctly.

If using ArrangeData the NULL data has been converted wrong. I am currently in Australia Eastern Daylight Saving (AEDT) time zone and I just recalled the NULL date is working fine back to October last year before daylight saving on.
But for a non-NULL date we can the date time is displayed as expected with same result in both ArrangeData and JSONSerialize.
Does anyone encounter similar issue?

Regards,
Soon