On January 21, 2019,

>! there was a [lunar eclipse](https://en.wikipedia.org/wiki/January_2019_lunar_eclipse); the totality phase lasted one hour and the 'full moon moment' happens during that hour.

On May 7, 2020,

>! the sun rose at 6:40am local time, five minutes before the 'full moon moment'. At the same moment, the moon set. If you had an unobstructed view, you could see both happening at the same time, proving that it was full moon at that moment or very close. (How close would still need some calculations.)

On March 1, 2018,

>! the reverse situation happened (compared to May 7, 2020): the moonrise happened about the same moment (6:14pm local time) as the sunset.