My Thermostat Is Messed Up

Okay, so this post doesn't rank high on the relevancy meter...but can someone explain why last night, when the thermostat read 76, I was freezing cold, and tonight, when it reads 72, I need to open the windows and cool the place down?

The weather outside is the same. I'm dressed the same. I'm doing the same things in the same places.

Oh well...it's nice and cool now.