Just to add – from what I recall from the past, there were people who would still celebrate Yom HaAtzmaut on ? ???? even when it was officially pushed off to ? ????.
If you say Hallel because you feel that a ?? happened on ? ???? that requires that Hallel be said, then logically it should be said on ? ????. The same would go for a Seudas Hodayah.
Although I would imagine that there some Frum people who don’t hold that way and DO say Hallel and/or have a Seudas Hodayah on ? ????.