How is it possible that I gained 2 kilos in a day?

It is possible. I just returned from a monster weekend getaway in Tokyo with my wife. It was our first trip away from the kids so I decided to eat with reckless abandon. It all started on Thursday afternoon at the Hong Kong airport where I was eating and drinking my face off and it did not end until Sunday night on the flight back home (still drinking cheap airplane wine and eating crappy airplane food)I did not get in a single workout (I don’t count the walking we did while shopping) nor did I count any calories or track any macros the entire time. The only thing I did was continue my IF protocol of skipping breakfast which is second nature to me at this point. It was a weekend of pure indulgence and utter freedom.