Don’t think Trump created one, he spoke or issued a statement on a day already set to honor victims of communism.

https://trumpwhitehouse.archives.gov/briefings-statements/presidential-message-national-day-victims-communism-2019/

And, yes there is a day for the remembrance of aborted children.

https://nationaldayofremembrance.org/

I personally knew a WWII veteran whose unit liberated a concentration camp. He didn’t talk about it much, but two parts of the story stuck out to me as a kid. The first was he and a team had to go through rail cars full of people who were killed in the camp right before they took over. He said the cars were crammed full and all they could do was estimate.

The other part of the story was most of his unit were so deeply affected by what they saw and many lost their appetite to a point they lost a significant amount of weight even though they were already very fit.