First Day Mishap

So here's my first day on the job at the new company, and I thought everything was going smoothly. But then it happened, in a meeting with all of my new coworkers, as we were reviewing the team schedule for the week, I accidentally said out loud that I had to leave early tomorrow because of a ‘dentist appointment’ when really I had meant to say ‘parent-teacher conference.’ Of course, no one questioned me about it, but now every time they mention leaving early next week, my face turns beet red and I just want to crawl under the table. I keep trying to correct myself by saying there’s an important meeting at my kid's school or something, but I can’t seem to remember which day is actually the conference versus when I go to the dentist for my regular checkup. It’s driving me crazy! And now everyone must think I’m so disorganized, I really am trying my best to fit in and not make too many mistakes.