The reality star sounded off on Saturday -- a day before International Transgender Day of Visibility, which just so happens to fall on Easter this year -- and took aim at Joe specifically ... as it appears she believes he might've made one land on the other on purpose.

She writes, "I am absolutely disgusted that Joe Biden has declared the most Holy of Holy days - a self proclaimed devout Catholic - as Transgender Day of Visibility. The only thing you should be declaring on this day is ‘HE is Risen’."

Of course, the irony here is ... well, CJ herself is transgender -- and yet, she's very angry about this. The other strange thing is the fact that JB isn't actually responsible here.

Fact is ... the TDOV has been around since '09 -- when Barack Obama was in office -- but it seems Caitlyn, and other conservatives, are reacting to an official White House proclamation that got posted this week, which does seem to make it sound like Joe's the one enacting it.

It reads, "NOW, THEREFORE, I, JOSEPH R. BIDEN JR., President of the United States of America, by virtue of the authority vested in me by the Constitution and the laws of the United States, do hereby proclaim March 31, 2024, as Transgender Day of Visibility."

It goes on ... "I call upon all Americans to join us in lifting up the lives and voices of transgender people throughout our Nation and to work toward eliminating violence and discrimination based on gender identity."

Again, Joe and co. aren't the ones who initiated the holiday -- but they're certainly spotlighting it ... and in light of some controversy at the White House of late pertaining to trans people, it would appear the right is fired up over the fact it falls on Easter Sunday in '24.