Applied at McDonald's for Unknown

I had an interview with McDonald's yesterday for a position, and they mentioned they would get back to me by the end of the day regarding a second interview. However, I haven't heard from them yet. I'm debating whether I should follow up with an email today or wait until tomorrow. Part of me thinks I should give them another 24 hours to respond, but I also don't want to seem too eager. I'm looking for advice on the best course of action.