Were you actually in those countries or just connecting in airports that happen to be located there? The latter doesn't count IMO.

Getting three wasn't too hard with StarMegaDo as we had parties in Germany, Norway and France on the same day and that was more than just airport connections. Also possible was USA-Panama-Mexico on the recent CM H-fare sale. I did that twice earlier this year, visiting the Panama Canal both times before heading on to Mexico City.

My other 3-country day started in the USA then went to the UK overnight and Luxembourg later than night. All in 24 hours but had the overnight of the red-eye to miss the calendar-day requirement.