@DustinB3403 We also just drank from the keggerator today. The beer was paid for/made/delivered a while ago. The beer that people drank on Wednesday was Wednesday's beer. The beer that they drank today was Friday's beer. It's pretty simple.
Same idea with an event. If I schedule a meeting for Thursday but nobody can attend the initial time so I change it to Friday, it is then Friday's meeting.
Think of it as each day being an actual person. If Mr. Thursday has pizza, then he leaves and gives it to Mr. Friday, it is now in Mr. Friday's possession and is therefore Mr. Friday's pizza.
Say it's illegal drugs. If Mr. Thursday has a bunch of illegal drugs. Then he hangs out with Mr. Friday, and when Mr. Friday leaves he has the illegal drugs in his possession. On his way home, Mr. Friday gets pulled over by a police officer who finds the drugs. Mr. Friday isn't going to be able to get away with saying, "Oh no, these are Mr. Thursday's drugs."
Regardless of initial intent, it is now in Friday's possession.