Swapping calendar items

Brooke suggests that we calendar our time at least 24 hours in advance and to honor our commitments without moving things around last-minute. Since I started doing this, I’ve been so much more productive!

What I’m wondering: Is it ever appropriate to swap around calendar items last minute? For example…

Let’s say that on Wednesday evenings, I have calendared in house work (laundry, etc.). On Saturday evenings, I have free time that’s available for hanging out with friends, watching Netflix, etc. On Wednesday afternoon, a friend asks me to come over for dinner that night. Is it appropriate to say yes and to swap my Wednesday/Saturday plans? Or should I say no, because it’s a last-minute event and my prefrontal cortex wasn’t involved in deciding on dinner on Wednesday night?

Thanks in advance for your ideas!