When did you first leave your baby overnight?

My husband and I are planning a 3 night getaway in the fall. My daughter will have just turned 1 year old, and my MIL is planning to keep her. We live about 7 hours away from our families, so she doesn't see her grandparents super often, although I'm pretty sure she recognizes them. I've never left her overnight and am really concerned. She's stayed with my mom for an entire day (morning all the way until bedtime) and was completely fine. When did you first leave your little one overnight? How'd they do? I'm nervous about it, but we could really use a little time away! :)