Accidentally scheduled a work event on Rosh Hashanah, feel like an idiot

I forgot when Rosh Hashanah is, and scheduled a work event on it

For context, I was not raised Jewish, but I connected with my Jewish heritage in college, was in a Jewish fraternity, went to Israel, did a Jewish learning class etc. When the topic of my background comes up at work, I’ll say I’m Jewish from (middle eastern country) because that’s my ethnic background. But I don’t really practice Judaism… my parents and immediate second family don’t, and I just feel too busy with life and grad school to engage with it.

So that leads us to now… I’m planning an important event at work where we’re inviting people tons of people from different companies to attend. I picked Thursday, October 3 as the date because there were limited options. I’ve got grad school and a busy work and I didn’t even think to take any of the holidays off so it didn’t occur to me (and any of my other colleagues for that matter, albeit non Jews) that it was on Rosh Hashanah.

Of course, a handful of people I invited said they couldn’t attend, including an old boss of mine who gave me shit for it (playfully but still annoyed). So obviously I feel like a complete idiot because I’ve been telling my coworkers that I am Jewish but now I’ve just scheduled an event over an important holiday that I’m clearly not observing.

Has anyone ever experienced something like this at work before? Or just been in a similar situation? I honestly just feel like a huge idiot and also disrespectful.